Day after B12 injection : I’ve recently... - Pernicious Anaemi...

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Day after B12 injection


I’ve recently had a b12 injection at my docs and the following day I felt absolutely knackered. Heavy hot feet, no energy. The nurse always asks me if I get a good feeling after the injection, but unlike everyone else she sees, I don’t. Is this normal? It happens each time and I’ve been getting injections for over a year. I also self inject in between, and I’m always so tired?

41 Replies

Now that I’m on the right injection frequency for me (twice weekly) I find that I don’t feel any different at all from one day to the next.

If you’re always tired maybe it’s time to consider if your injection frequency is sufficient or other possible reasons such as thyroid or low iron?

I’ll have to ask docs for thyroid iron check but if they do that blood test they’ll see my b12 is well ok and my worry is they’ll stop it as they ve done to others

Nackapan in reply to lizblow

You dont have to have your b12 done.

The only time its tricky is if you want tour folate checked as that is done with b12

I had my thyroid iron vit and others done but not folate or b12 recently

I rarely do either . Its happened once I think. My daughter stays on an even keel until the next one due and then she gets fatigued and gets the benefit quite quickly with no ill effects.

I've never had that pattern.

Symptoms all over the place.

I'm just worse/ill if I dont have it. . My balance goes . I get very very weak . Cant stand ect. I've bad fatigue .

What is better after 21 months is I dont often have a headache after it any more. Or terrible tinnitus I always feel knocked our though . Bit ' out of it.'

A few occasions hoping to pick up or feel more energy . I dont but would get ill without it.

The nurse asks me as well .

I am still waiting for the skipping down the road feeling I was promised by the doctor in Nov. 2018

I used to get lead legs after an injection too but rarely now.

The benefits for me kick in

2 to 3 days after. I'm up until 7pm or even 8pm! I dont go to sleep but cant operate anymore so have to sit in bed .

So doyou feel worse than before you had it ?

lizblow in reply to Nackapan

I’m always tired but noticed a dead feeling especially after my last one. I was expecting more and always will hope to feel normal one day

How often to you have injections?

lizblow in reply to Nackapan

It’s so funny as I every 3 months, now I thought 3 months was 12 weeks but apparently not. I went 12 weeks later and got refused by the nurse and had to wait another week. My doctor also didn’t understand that 12 weeks isn’t 3 months!

But I do self inject on the quiet in my belly but they do it in my arm. Is there a difference?

Nackapan in reply to lizblow

How annoying.

So in other words you are being under treated.

Good you keep a better regime with injecting at home too. You can Google injection sites for IM and SC. There are clear pictures.

I also do that but far more frequently at home going less to the surgery . Leaving it 6 weeks this time for nurse appointment and IM. (Usually 2 weekly)

I do SC at home. I use 30G 1/2" which is fine. Bought my needles sharp box syringes and German b12 (with help from here)

Eventually got for a prescription from GP too . Just for b12 ampoules.

Just as well really as had the kit already!! Much cheaper than a prescription. I wanted it on my medical record. Hopefully have all SC. Still monitoring to see if any difference . Keep copius notes.

You could ask for a prescription

IM is easier to get as licensed . The nurse would instruct you I ecpect.

There are different options . We are just not told them at the surgery.

Hope you having a regular frequency that hopefully will give more relief to symptoms.

There’s no difference at all . B12 can be injected I.M. ( intramuscularly) into the arm or the middle outer third of the thighs, with a 25G x 1 inch needle — or sub -cut ( Subcutaneously) into the stomach or thighs with a fine short needle say 30G x 1/2 inch .

Sorry to jump on, but would I dread self-injecting less do you think if I used a 1 inch needle (I do thigh). I bought 1.25 inch as was following what someone else did on another group, but I am much slimmer than that person. Been doing SI since April 19. Or even try stomach as have so many veins visible veins I try and avoid on my legs. Subcut being a finer needle is it harder for B12 liquid to go through.

Unless you are overweight , a 1inch needle for I.M. should be fine .If you use a 1.25 inch needle, then don’t insert it completely . You can use sub-cut into your thigh or stomach .

Yes a 30 G x 1/2 inch is fine for sub-cut , but yes, the finer the needle , the longer it will take to inject , but not much longer !

Ah, thank you for that info. I have a lot of needles to use up, I bought 100. Ok, I will try not inserting it completely in. Didn't know you can do sub-cut into thigh. Is it much easier with 30G into stomach. I only started IM as I thought I read it gets round the system quicker or something.

Yes , “ they” do say that I.M. gets into the system quicker , but if you have recovered from your deficiency ,I can’t see that matters at all . I use I.M. for my injections. I’m so used to that after 4 years . I didn’t realise when I started Injecting that one could use sub -cut for B12, or I might have used that method . I did eventually notice on the packets of B12 Ampoules that I get from Germany, that they could be injected subcutaneously. Then I read that some people on this forum use sub- cut into the thigh . I think that would be more painless than into the tummy . Also a large surface area, using both thighs. But google it , and you will get a bit more information .

Thank you, I will have a look. Are you used to IM - I suppose you must be. My very first one was totally painless but I seem to have gone downhill with them. I have so many thread veins on my thighs and veins that look near the surface I am always afraid of where to put the needle. I have watched videos and looked at pictures of where to inject. I always thought it was side of the thigh, but I saw a doctor injecting and he used more or less top of thigh - is there a right place, where do you put the needle ? I know it is middle third of the thigh.

I always use the outer middle third of my thigh and don’t have any problems . Over 4 years of injecting weekly , only ever had a spurting of blood 2-3 times , which I just stopped by pressing on it .i don’t get any pain at all , just an odd sensation sometimes . But I’m not familiar with sub-cut at all .

Yes, I have been doing outer, then read somewhere a nurse said that would hurt and a video showed more towards top, so I got confused. It often stings as I put needle in, but it helps if I sing! Someone I know has graduated to arm IM, but I don't think I could manage that, I have to hang on to the syringe with two hands as it is!

Arm is definitely not the best place to use for self- injection .You would always be using the same place , unless you are ambidextrous

Better for the skin not to continually use the same place . Easier to inject at 90 degrees using the thighs for self-injecting . Nurses use the arm because it’s the most convenient . . . Not so much undressing involved ... .You have a much larger surface area to use when injecting the thigh . I keep a note of which side I’ve used last ! And alternate .

Yes, I also keep a note - actually a spreadsheet with injections and also symptoms plus a Word document about health too. I also massage the area with body cream (when I think about it!).


Hi, I have my injection at 8-9 weeks at gp surgery but also self treat with injections in between.

My husband noticed that I always feel unwell for two days after my NHS injection.

I hadn't realised because I am used to off days with my ms.

He says it is obvious.


lizblow in reply to ellj

Sorry to hear that but I’m glad I’m not the only one x there must be a reason ..??

Cd123 in reply to lizblow

Hi. I always feel rubbish for the first two days after my injection. Worse than before but then pick up, usually on day three. I am on four weeks.

Nackapan in reply to Cd123

I pick up on day 3 too . My theory as having IM and SC is IM goes into my system quicker. Sometimes with overwhelming symptoms sometimes with very little?? I always though on the day after especially feel unwell.

I thought at one stage it was different brands. This now does not seem the case. I braved it SI the brand I was prescribed and thought the culprit I was fine I think different administration does come into it.

Only my opinion.

Nothing is consistent with this condition it seems.

Nackapan in reply to ellj

Same here

Have you tried potassium? I think gets depleted by the influx of B12. I don't use tablets, I use potassium gluconate in water to yield about 400 mg K. Coconut water or low-sodium V8 also works and is easier to find.

fbirder in reply to genesurf


Potassium levels can drop during the first few weeks of injections only. And only if you had been suffering from macrocytic anaemia. After those first few weeks potassium levels are not affected.

Nobody should take potassium supplements without a doctors knowledge as too mach can be very harmful.

tesla20 in reply to fbirder

Can this be explained? Why would it drop only in the first few weeks and not after, even though you keep doing the injections? Won't it depends on how often the injections are being done, eg. daily, weekly, monthly?

"Potassium levels can drop during the first few weeks of injections only. And only if you had been suffering from macrocytic anaemia. After those first few weeks potassium levels are not affected".

fbirder in reply to tesla20

Low potassium (hypokalaemia) can happen you have macrocytic anaemia, caused by low B12 or low folate. When the body gets enough B12, or folate, whichever was the cause, then it starts a program of making lots and lots of new red cells (reticulocytosis).

This rapid burst of cell formation needs a lot of resources. Most of them, like iron, the body has in abundance. But the body doesn't store much potassium (presumably because it can be harmful). So the burst can, temporarily, deplete potassium to a significant level.

Once that burst is over then red cell formation continues at the same rate as in normal people. And your potassium requirements are the same as a normal person.

It's not the only way of getting low on potassium. I was on a drug trial about 40 years ago and was told I needed to lose weight before I could do it. I lost several pounds in a week and was told I couldn't do the trial because my potassium was too low. I knew, but that doctor didn't, that rapid weight loss can cause hypokalaemia. So I went to see the doc in charge, who told me that the first doc was an idiot.

Nackapan in reply to genesurf

My potassium level has been checked several times soon after an injection.

It's okay.

Potassium is safer sourced from food.

Any potatoes , bananas ect

I used to go to bed for a day and a half after every injection. I’m almost three years into treatment and finally have weekly injections and I rarely have that fatigue anymore. Good luck to you. Hopefully it will get better.

Nackapan in reply to Emmers5

Thars reassuring as I'm a year behind you .

I'm presently trialing 5-7 day b12 I jections . Was on 2 weekly for the lady year. Tried 3 weekly a few times but realise probably went in the wrong direction. Felt under pressure from Gp to try going longer between on b12 tablets 50mcg as well.

Well I tried and actually disappointed her plan did not work.

mountainice in reply to Nackapan

Are u trialling through GP do you mean?

Nackapan in reply to mountainice

No Gp prescribes 2 weekly for the last year . I'm trialling 5-7 days with extra I've bought .

I'm done with tablets sublinguajs ect. But I had to try as do help some .

mountainice in reply to Nackapan

I may have a battle on my hands as GP says there is no evidence to say we can have monthly injections - she is trying to stop them.

Hi, it’s just a thought, have you had blood sugar levels checked? I’d been going for years to gp with exhaustion, they tested liver kidneys and thyroid, kept telling me I was depressed. A few years on, Dermatology tested blood sugar before prescribing meds for abscesses and found I was diabetic. Once that was properly treated (a year plus on) I was still exhausted and finally found I had pa too. Initial treatment didn’t do that much as it wasn’t enough. Now I self inject weekly and I am no longer exhausted. Also other symptoms I hadn’t thought were linked subsided (tinnitus, crawly scalp, muscle twitches, pains in arms and legs, numb toe, pins and needles in fingers, memory and concentration problems). It’s hard when you’ve no energy to keep at it , but do- when you find the right treatment and levels it’s so worth it. I had no life, just work, eat, sleep excessively. Now I’ve got my life back x

Nackapan in reply to earthnymph

Glad you found a solution. Surly blood sugars should've been checked!! I despair.

Theres no way I can work. I've a long road ahead still.

earthnymph in reply to Nackapan

Thanks Nackapan, and keep up your good work on yourself , I hope you get where you want to be soon x I honestly don’t know how I kept going, I don’t think I could have lasted much longer. Partly it was determination to prove wrong the people who thought I was completely potty (docs, parents, sibling etc). Yes it should have been checked, it had got very bad before it was found. There is still a tendency to write off what women assert as histrionics etc. Particularly if like me you have had a bout of severe depression years ago. Very glad I got sorted or I would have been dead now. Really. Everyone struggling please keep at it, I know it’s extremely hard, but eventually they have to listen. Eventually you get to the right treatment even if it’s taking matters into your own hands. Once you start gaining strength in body and mind the battle gets a bit easier x

I always take it easy for 2 days after injection and then feel much better. I ensure folate, magnesium and potassium intake is optimum. I self inject between GP jabs so can't explain, I have decided it takes time for my body to absorb and utilise it and rest helps.

Hi. I’ve had PA for 18months now and have injections every three months but I don’t feel any different. Yet my nurse continues to tell me that others feel amazing after their injection. I’ve also graves’ disease, which is in control just now and I also suffer from low ferritin and get a ferinject iron infusion every six months for but even when graves is ok, b12 is topped up, and iron is topped up I still just feel the same. Main symptom for me is fatigue and brain fog.

JanD236 in reply to ickyrocket

Ickyrocket I have Graves and PA although as far as I know my iron is ok. I just wanted to say that when I was on 2 monthly injections I never really felt any different either, maybe just a bit more tired in the run up to the next shot. Because of that I asked the GP for monthly injections and fortunately he agreed. I began to notice that I definitely felt better for a while after the injection so I started si, first weekly then twice weekly. I now feel pretty good all the time.

It probably took me 2-3 years from my first bi monthly injections to settling on twice weekly. I now lead an active sporting life which I very much appreciate and enjoy.

ickyrocket in reply to JanD236

That sounds great, I just wouldn’t know how to about getting injections monthly and I would have the worry they would stop them if I tried.

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