B12 loading dose - am I just being impatient?

I'm almost at the end of my loading dose (I've had 7 out of 8 injections over 4 weeks) and not have felt much improvement. I've had a slight improvement in strength levels, but nothing in the way of energy. After my last injection later this week, I'm being moved to the three-month regime.

I keep thinking about buying supplements to see if that will improve things any faster, but I don't know if I simply need to give the injections more time to work. It doesn't help that I'm also hypothyroid (diagnosed at the same time as B12 deficiency) and have no way of knowing how much of my continuing exhaustion is due to the fact I've been on 50mg thyroxine for only three and a half weeks.

I keep going round the circle of "Well, I can't overdose on B12, so what harm would it do to get some sublinguals", and "Would I just be wasting my (extremely limited) money because I'm impatient"? I'd *really* welcome any advice!

The GP surgery has no intention of measuring my B12 levels again at any point "Because we know the injections work". So taking supplements now wouldn't skew any treatment I might receive in the future - I've been told I'm on injections for life, though haven't been tested for PA, which has left me a little confused. Oh, and I have no idea about my folate levels, which I understand need to be decent in order for the B12 to work properly. I'm going to ask to have it tested when I go back for my thyroid test in another two and a half weeks, though I have no idea how well that request will be received. In the meantime I'm taking a B-complex that includes folic acid.

Again, thank you so much for any help anyone is able to give.

38 Replies

  • Hi Impala ,

    I expect you have to wait a bit, particularly as you also have just started 50mg thyroxine for only three and a half weeks. Both B12 and thyroid meds can take some time to feel effective , in your case its just a double whammy , you must be feeling exhausted! Give it a few months, look after your self now, eat well, sleep lots, and hopefully you will feel a lot better in a few months (could be weeks we all are different).

    If not think then about spending money on self treating, I tried high dose of B12 tablets, lozenges etc, but they did nothing for me but empty my wallet.

    So much has gone wrong over years in your body, it is most likely going to take a few months for all to get right. It took me some 3-4 months to feel the benefit of B12 injections, but then it was really good and you then start to rely on the B12 keeping you well I know little about thyroid meds but believe they also take a few months to feel the benefit. Taking a multi vitamin can help to make sure you do not get to many in-balances, all vits etc need to be in balance ideally. Giving loads of one can cause others to deplete, so a multi can help avoid deficiencies in other (B) vitamins occurring in the initial load up time that will mean a lot of new cells being produced in the body etc.

    I hope you will feel a great improvement though in time,

    Kind regards,


  • Marre, thank you so much for your answer. I think I was just about managing to hold onto 'this will take time' until I saw the nurse for my injection a couple of days ago and she expressed surprise that I wasn't really feeling any better. I came away thinking there must be a fault with my body's reactions to the shots and panicking about what would happen if my body wasn't getting any more B12 getting put into it for the next three months. That led to the rather unhelpful spiral of thoughts that ended up in my post.

    Your reply has helped me to understand better and accept that this *is* going to take time. I think I knew this, but I didn't really believe it. *grins ruefully*

    Very interesting to hear that the B12 supplements don't work for everyone - I'm sorry that's the case for you. Oh, and I have just started on what looks like a good multi-vit/mineral daily supplement - thank you for the tip!

    Thank you also for such a sympathetic and supportive response - it helps a lot. I'm sorry you had to wait quite some time to see an improvement yourself, but it sounds as if things are much improved for you now. I'm so glad. :)

  • Your doing all the right thing, and hopefully you will feel a lot better soon! Its just very different per person, some do feel the benefit of the loading jabs straight away, for others it may take some time, some really benefit with adding other forms a B12 preparations to their treatment, we all are different. I am very well now, but I did need to get some adjusting to my initial treatment after 5 years of trying to cope, and seeing a haematologist and neurologist helped me to get my treatment right, plus learning to self inject. Hopefully you will just be fine soon!

  • Thanks, Marre! It's so helpful to know that not everyone responds straight away, and also wonderful to hear your (eventual) success story. :) I realise there may be more adjustments to be made before I get sorted out, but I realise now I need to give this a chance to work first rather than trying everything at once, because then I'll never find out what *does* work! :)

  • The test for PA is notoriously hit and miss as it isn't very sensitive and it doesn't actually matter what the cause of your deficiency was the treatment is the same (unless it is down to lack in the diet) - shots of B12.

    The deficiency basically happens because the delicate mechanism that absorbs B12 in the ileum goes wrong but there could be a number of reasons for this

    - an autoimmune response (body creates antibodies that either destroy intrinsic factor - a binding agent necessary for the process) or the parietal cells (which do the actual absorbing). This is PA in its proper sense

    - if the ileum has been removed or changed by surgery then the cells needed for absorption will no longer be there so ...

    - as you get older levels of acid in the stomach decrease - and the body needs a certain layer of acidity in the gut to be able to process B12

    - there are also some drug interactions eg Proton Pump inhibitors that are used to lower stomach acid and treat heart burn/acid reflux, metformin used to treat diabetes (though some research shows that although it lowers absorption it may increase the efficiency of metabolising ...), NSAIDs (eg ibuprofen) ... and a load of others.

    - congenital deformations in the ileum

    I think you could actually drive yourself mad trying to get to the bottom of what actually caused the deficiency - though I also think there is a case for GPs being more aware of drug interactions as in theory resolving those should correct the deficiency but as things like acid reflux can be symptoms of an underlying deficiency occuring there is also an argument that that is a bit of a mute point.

    The bottom line is that whatever the cause the treatment is the same - finding another way of getting B12 into the body that doesn't involve the gut - and injections are the most efficient.

    Depending on what symptoms you have a couple of weeks is probably a bit early. The first time I noticed energy levels rising from B12 was when I had a B12 shot about 9 months after my loading doses - which doesn't meant that it wasn't there just that I hadn't noticed because I was just told my B12 was low to start off with without any explanation of what that meant.

    Given the other complications I would probably wait and see what happens with getting the thyroid problem sorted out before putting too much financial resource into supplementation - but do keep a record of how you are feeling as there may be symptoms that you haven't really noticed that the B12 has been helping with that you'll notice returning before the next shot.

    Really hope you feel better soon

  • Sorry meant to mention - people vary very much in how long they actually retain B12 - so sometimes testing can be appropriate where symptoms are returning quickly as it can show that you do need more frequent injections to keep levels high. However, the test isn't that good a guide and a high results mean nothing, though can cause a lot of unwanted attention and treatment being withdrawn when it shouldn't be because of mistaken assumptions that too much B12 is bad.

    In some ways dealing with the thyroid is easier as test results are more accurate measures of what is going on.

  • Thanks so much for answering, Gambit. I'm sorry you had to wait so long to see an energy improvement from your B12 shots, but from my perspective that's incredibly helpful to hear. I know we're all different, of course, and all starting from different places, just to complicate matters further, but I've been grappling with trying to get *some* idea of how long it might take to see a clearly noticeable improvement. I should be rejoicing in the slight increase of strength (which I did for a few days, until I started to get used to it), rather than focusing on what I don't yet have!

    I take your point about driving myself mad trying to understand the cause of these conditions. I have been telling myself it doesn't matter if I don't have a label to put on it, but then I read the various guidelines and wonder why the doctor didn't investigate further re the cause of either condition. I've thought perhaps they get to the point where they see these things presenting together so often that they don't want to waste time and money just to slap a label on it that doesn't affect the treatment, perhaps. Anyway, that's speculation. The point is, as you say, treating the condition, and from what I've read of some people's experiences, I'm very fortunate to have a doctor who instantly said I'd need injections for life.

    I'm trying to keep a symptom diary, but some days it seems like a bit too much effort - you've reminded me how important it actually is, so thank you. And thanks so much for the guidance re supplementation, which makes a lot of sense. I will save my money for now. :)

    As I said to Marre above, your response has helped me to understand and believe that this is going to take time to sort out. Of course this little part of me still hopes I'll wake up tomorrow and magically feel better, but I think as long as I don't get disappointed when that doesn't happen, that's okay! Thank you so much for your detailed and sympathetic answer. I hope you're continuing to feel better.

  • Whilst I didn't feel anything for many months that was the point at which I really noticed the shots having any effect for the first time - I then realised that if I was to really get better I obviously needed higher B12 levels than I was achieving on the regime that I was being given but couldn't get my GP to listen which is when I started really treating myself and is also the point at which I really got my life back after so many years it's incredible. Just see how it goes - get the thyroid sorted out and then take it from there.

  • Wise counsel indeed - thank you!!

    I'm glad to hear you have your life back, but very sorry it took so long.

  • Hello. Have just stumbled across your post from two years ago. If you're still on here, could you please tell me how long it did take, as I had 9 loading doses in April, but am still awaiting any improvement!!

    Thank you 😊

  • Hi, I'm sorry to hear you're still struggling. Other people on the forum know much more about these things than I do, but I would look into getting your folate, iron, and Vit D levels checked. I believe your body needs a decent level of folate to utilise the B12, and if you are having B12 absorption problems, it *may* mean you're having problems absorbing other vitamins and minerals. For me, supplementing Vit D, iron, and magnesium made a big difference to how I felt (my magnesium blood test showed a decent level, but I kept getting muscle cramps which disappeared once I started supplementing, so blood tests aren't the whole story with some of these things).

    But to (finally!) answer your question - I'm afraid I'm still waiting to feel better! Before you get too depressed, I am *not* a straightforward B12 deficiency case as I have other medical problems that have subsequently been discovered (mitochondrial dysfunction, as well as the ongoing saga of trying to find the right treatment for my thyroid issues).

    I'm sorry I can't really help you out, but as I say, there are some extremely knowledgeable people on this forum with a great deal of experience about B12 and I hope some of them will be able to help you if you make a new post.

  • Thanks for your answer. I have had all the other levels checked, but useful to hear about magnesium.

    Sorry to hear you're still unwell. It must be difficult to manage several conditions & get the balance right.

    Wishing all the very best.

  • Thanks so much for the good wishes, Ajane, and I do hope you start to see an improvement soon. I know some people say that it takes time for B12 to repair any damage that's been done by low levels, so I wonder if that may be part of what's going on with you. Also, I don't know if you are supplementing while waiting for your next injection; it may well be worth trying that as the injections are not often enough for many of us with this lovely condition. I hope you start to feel better very soon!

  • Hi Impala, I'm so sorry to hear you have to deal with both conditions at once! You must feel so exhausted. I'd been hypothyroid for some years before I discovered I'd got low B12 too. Unfortunately both of these conditions have similar symptoms, so it's really good that your GP picked them both up. It will take a while until your thyroid is optimally treated ( the 50mg of Levothyroxine is only a starter dose). Usually it will be increased gradually by 25mg at a time, with interim blood tests to check how things are going. I am rather surprised that the GP is not planning to do anymore B12 testing though. Again, they usually monitor how much B12 is being retained by testing six to eight weeks after the loading doses. Have you got any neurological symptoms from the low B12? Numbness, pins and needles, memory problems etc....? Hope you get all the help you need, people on here are great at advising and providing links to further information. Best wishes MariLiz

  • Hi MariLiz. I'm sorry to hear you too have both conditions. I hope you're doing okay? Yes, I feel very lucky that the GP picked up both conditions; in my case, I started to suffer from almost constant migraines, having never had them before, and thankfully the doctor took them seriously. Oddly, they tailed off just before I got a diagnosis and started either treatment. I have no explanation for that as I changed nothing in my diet or lifestyle (which at that point was shuffling between sofa and bed!), but I'm deeply thankful for them as they led to this diagnosis.

    I'm one of the very fortunate few who don't seem to have neurological symptoms, though my level is 158. That doesn't mean there hasn't been damage done, I realise. My main symptom is overwhelming exhaustion, with a few other things like intermittently aching joints and tinnitus thrown in. I have memory lapses - things like pouring cold water onto instant coffee because I forgot to boil the kettle, and an inability to find the right words quite frequently, but they may well be a result of the tiredness as much as anything else.

    I think one of the things I'm most puzzled by is knowing which symptoms are due to which condition; I don't know how I'll be able to tell if the B12 levels are getting low again, and that's why I was a bit surprised at the lack of future testing of B12. I guess I just need to get on with both treatments and see where they take me, rather than dreaming up issues that may never come to pass. :)

    Thank you so much for the help and good wishes. Your guidance about the thyroxine is also very helpful - I think I was being a bit unrealistic in my timescale, especially if 50mg is just a starter dose. I'm sorry you too have this struggle.

  • Hi, I've recently just gone through all this too so hopefully I can help you a bit. It took me about 6 weeks after the loading doses to feel better. I'm usually exhausted all the time and what happened was I started my Christmas holidays from uni and then went on an active long weekend holiday with friends and when I got back from that at around 9 at night I was still feeling wide awake! It just sort of happens gradually without really noticing at first that suddenly you can function again. I think what also helps is giving yourself time to properly relax after the injections. When I was getting my loading injections I had university exams and I felt absolutely awful. I think it was after spending a week relaxing at home in my holidays that gave my body some proper time to recover which really helped.

    Did your nurse tell you you would have them for life? I found that a lot of nurses and even some GP's get confused about this as they tend to think PA and b12 deficiency are the same thing but they're not. What generally happens is that you will get your b12 injections for around 2 years then they will retest and see whether you should continue them. They will not give you life long injections if you haven't even been tested for PA. Folate is usually measured with b12, is it possible that they tested it without you knowing? Either way its a good idea to take your B complex while receiving the injections.

    Hope you feel better soon!

  • Hi Carly, and thank you so much for your really helpful and hopeful reply! The doctor said I'd be on the B12 injections for life even though I haven't been tested for PA. I think I'm just going to take the life-long prescription as a win; I know how hard other people have had to fight for it and think I've been very lucky in my GP.

    I got a print-out of my blood tests, and there's nothing on there that says folate. I think I've tracked down what all the other tests were for on google, and none of them are for folate either, so it seems that for whatever reason they didn't test.

    Thank you again for the help - it makes such a difference to hear actual timeframes in which people started to feel better, not least to see how different they are for differnt people. :) And I'm so sorry you went through this while facing exams at uni. I have no idea how you coped, but you have my absolute admiration.

  • Your comment about having injections for two years and then being retested to see whether injections are still required is nonsense. PA is just one specific cause of B12 deficiency and the treatment for any B12 deficiency, unless caused by diet which can be corrected, is injections for life. Nowhere in any guidance to doctors is it suggested that injections should ever be stopped.

    The B12 blood serum test is useless and should never under any circumstances be used to determine the frequency of injections or whether they should be stopped. The only guide to injection frequency should be the patient's symptoms.

  • That's what my endocrinologist said. Basically he said that they test the b12 to see where its at after about 2 years and see where we go from there. I'm not a doctor so I can only pass on what the specialist said... My gp said that the most common cause she saw of b12 deficiency was diet (despite officially the most common cause being PA) and this wouldn't need life long injections if the diet can be fixed.

  • They are both wrong.

  • My doctor was skeptical about my complaints that B12 was running out early. I also noticed that some symptoms repeated after each jab that were similar to the symptoms before the jab.

    I kept a daily log of my symptoms, the food I ate and drank, my meds and the physical exercise and other stressful events in my daily routine.

    I was sorting through a gluten and dairy intolerance along with issues with drinking wine or any alcohol of any amount. I also was developing photo sensitivity. All the symptoms from food and meds were delayed between 6 and 24 hours because the gut was involved. Stress just accelerated my consumption of B12.

    The log / diary / journal / excel spreadsheet - what ever you want to call it - provided a memory jogger because I was also having short term memory issues at the time. It helped me also sort through the symptoms from the jab that repeated regularly after each jab. This also helped me to de-stress, calm down and take control of my situation.

    The symptoms right after the jab were worse when I was low on B12 before the jab. PAS also helped me indentify these symptoms as detox issues. The lower I was on B12 before the jab, the larger the symptom after the jab.

    The log became evidence for the dr that I was monitoring my conditions very closely. I invited him to keep a copy in his records but he declined. After about the third time he agreed to increase to 8 weeks and finally to 4 weeks for hydroxocobalamin.

    When I moved to the USA and switched to cyanocobalamin, I used the same technique to convince my new dr that I needed more frequent injections.

    I moved from 30 days to 14 and then to 7 and I finally started self injecting and my dr has basically said I can use what I need but the pharmacy now is the choke point because the dr can only write a prescription for 1 jab a week. They issue me 4x 1 ml per month and won't let me refill any sooner. I ended up splitting the jab into two 0.5 ml on Sunday and Wednesday evenings.

    I switched to the evening to be able to sleep off a headache symptom following the jab. Now with my current regime, as well as supplementing with folic acid, a multivitamin, Vit B6, and biotin, and the occasional methyl-B12 sublingual before a stressful meeting, the roller coaster ride of symptoms has leveled off.

    Folic acid in particular is needed for B12 to work. Look up methylation loop. You may feel tired because you have used up any existing stock of folate in your body when your loading doses started.

    Neurological symptoms are very slow to correct. I think I have suffered some permanent nerve damage in my right hip which may never go away and I now have tinnitus pretty much all the time.

    The main thing f orme is that with this fairly complex maintenance regime, the nerve damage is not getting worse.

    My energy still goes up and down and I find just getting started is the hardest. Regular physical exercise helps get the injection out of the muscle and into the blood stream. Once I get going, and I pace myself, I'm pretty much good to go and feel better.

  • My apologies for the long delay in replying to you - I've had a pretty lousy week or so in terms of energy levels. Thanks for your detailed answer; the bit about symptoms after the jab being detox are particularly interesting to me, as the first couple of jabs I had gave me migraines and knocked me out for a couple of days afterwards. I could see the pattern repeating, but getting milder, as the loading dose jabs continued. Now I understand what was probably going on! I also really do need to get my folate tested, I realise.

    Thanks again for all your help, and I hope you continue to be as well as you can be.

  • The detox symptoms will return in the future after a jab if you get too low in B12 before the jab.

  • Thank you - that's really helpful to know. One of the things I'm trying to puzzle through at the moment is how to tell which symptoms are down to hypothyroidism and which down to B12 deficiency; while obviously I don't want to get that low in B12 again, it'll at least be a marker of where my levels are.

  • I was diagnosed with pernicious anaemia 10 years ago so b12 supplements won't help me. But if you have a b12 deficiency they will . Make sure your diagnosis is correct as their is many forms of b12 problems that come under many names mega blastic for example . I was given 6 injection to be taken every other day as a starter and it took a good 6 weeks to feel better my levels were 56 should have been around 350-400 . They told me the damage had already been done to my lower intestine so only injections won't work as low b12 over a long period of time cause irreversible damage. I also have irreversible nerve damage in both feet and other issues. It's very important to get correct help and advise as some health officials just pass it on as it's easily treated without making a proper diagnosis good luck

  • Thanks, Vickie. I'm so sorry to hear about the amount of damage you suffered before diagnosis. I don't know precisely what the cause of my B12 deficiency is - the doctor said I don't have PA but when I asked if my deficiency was diet related, she said it wasn't, and that my gut can't absorb B12. I understand that people with hypothyroidism can have low stomach acid, which may have led to my B12 problem, though I confess I'm a bit uneasy about the fact she didn't at any point ask me about my diet or any other factors which might provide an alternative explanation. Otoh, I suspect she sees the hypothyroid/B12 pattern repeating over and over again.

    I'm off back to the doctor next week, and now have a number of questions for her. Thanks for your help!

  • Hi All,

    Recently i diagoned with Low B12 , that is 168 and go the first B12 injection this week. Started the feeling the pin and needle in feet, going to have few more injections in consecutive month. I read in lot of forums like low B12 can also cause hypothyroidism. DO i need to check for thyroid issues as well now itself or i can wait? In blood test i can see folate is normal but low B12, how much quantity of folate i need to take during few months of injection?


  • Hi Jana,

    Ideally you just increase your intake of natural folate (veg etc) but it can help to take an OTC muti vitamin as increased B12 will demand more of all other vitamins and minerals in your body, many vitamins need each other, particularly folate, B6 and iron are needed with B12 for good blood production. It is good to try to keep all vits in balance, which is what a multi vitamin does.

    It is common (up to 50%) to with PA/B12 def also to have thyroid problems and visa versa, but it does not mean that you have to have a thyroid problem, only perhaps have it tested if you are not doing well on the treatment offered,

    I hope this helps,

    Kind regards,


  • Marre,

    Thanks for prompt reply. I have one doubt now, My doctor told me 3 or 4 injections ..He told i can take any time i need. I am not clear about frequency. I took one injection this monday, can i take another 1 today (friday) or taking weekly once is safer ? I planned to take next on monday.


  • The norm for loading doses of hydroxocobalamin B12 injections is initially 6 injections; IM (in a muscle) one every other day, then go on to maintenance doses of one everyb 2-3 months. If its cyanocobalamin B12 the loading is different, maintenance different and same dcounts for methyl cobalamin. So firt you need to know what type of B12 you are injecting, how much, and then what is it for, diagnosis of what, why are you getting only 3-4? Very weird treatment. But it is safe to inject every other day, or weekly, or daily, depending on how much you inject and what way you inject; in a muscle or subcutain etc, to much B12 will just be weed out, so injecting daily if loads is just wasting it.

  • I am getting injections of Cyanocobalamine, but doctor told me weekly once 1 mg. He did say like 4 injections in one month, after 3 months of 4 injections then another test will be taken to check the B12 level. He suggested this since i am low in vitamin B12 - 168. I am blank now, must follow doctor. Good to see , we have people online to advise like you , Doctor's spend not more than 5 mins to hear their patients concerns, but your online information and posts are good.


  • Re: "weekly once 1 mg. He did say like 4 injections in one month, after 3 months of 4 injections then another test will be taken to check the B12 level", that is 12 injections once a week, sounds good, then retesting see how you are, all sounds good. It can take some time before you may feel the benefit of the B12 injections, but I'm sure you will, and it will make you feel a lot better I expect than you do now!

  • I really don't see the point of checking serum B12 after injections. All it seems to do if the result is in the normal range is to give the doctor the excuse to declare the patient "cured" and that any ongoing problems can not possibly be due to B12 deficiency. The only guide to the success of the treatment should be whether the patient's symptoms have improved.

  • Its both, 50/50, in the end for some a serum B12 test after starting treatment can be very helpful in seeing that one is not holding onto much of the B12 (in serum, my fathers serum B12 after loading was 136). Symptoms count as much. But blood tests are not only for testing serum B12, that may well not be done, it is to see if treatment is working, HB rises, platelet count may rise, MCH may drop, MCV should drop etc, if not other tests may then be done (such as serum folate, thyroid etc). That is how I think it works anyway.

  • marre,

    i checked my wife's blood tests, it shows B12 is 84 which is very low, and vitamin D is 15 which is also low. Her Folate is 6.8 which is good. She doesnt have any symptoms, just for comparison i checked her reports. Since she has more folate, B12 and D deficiency doesn't cause any issues? I think i need to check my Folate and vitamin D level.


  • Hi kuttipayyan ,

    OK I am confused now, in a previous post it says:"He suggested this since i am low in vitamin B12 - 168. ", now you are mentioning your wife has B12 of 84, is she on B12 treatment, who is the previous post for?

    Anyway folate can drop very quickly once B12 treatment has started so its worth keeping an eye on folate levels, as its quite common to become folate def once B12 treatment has started. ( my serum B12 was 86 ng/L = 63 pmol/L on diagnosis, folate fine, over time , 5 years, I also became folate def) . B12 needs folate and visa versa, many (B) vitamins need each other, giving loads of one can deplete others, so its all a matter of trying to keep a balance.

    Starting B12 treatment will not affect a vit D def as such, but any vit def should be addressed for complete recovery.

    I hope this helps,

    Kind regards,


  • Marre,

    Treatment is for me only. My health problem is Twitching all over the body. I doubt whether B12 deficiency is the root cause because i started having this problem when i got h.phylori in my stomach last year. After one month of medicine, i went away. I was ok for 6 months, suddenly one day i got fever and took Advil Gels, which caused my heart burn to come again and followed by Twitching. Either case it started when i had stomach problem. In India, 90% of doctors dont check B12 level and i beleive 50% of people could be B12 deficient by they dont have any issues. Just for comparison, i referred my wife's report which taken last year during her pregnancy time. She was deficient in B12 and D, doctor told her to take suppliments but she didn't take. She doesn't have any issues. Not sure, what is the root cause for my problem. i have gastro appoitment today. Lets see.

  • I believe B12 def is very common in India because of the mainly vegetarian diet and H Pylori is common unfortunately. The thing with H Pylori is that it can survive initial treatment with antibiotics (H. pylori antibiotic resistance ) so it needs to be checked that it has actually gone, but it also damages the stomach , it can leave permanent damage . I am sorry to read you wife had such a low B12 reading and only got supplements, hope she is OK and the child is OK.

    Perhaps read this it may help you decided what other tests may be of use to you, see:



You may also like...