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Pernicious Anaemia Society
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What should b12 levels be 6 weeks after injection

Hi, as above I has my b12 injection 6 weeks ago. Just had my levels checked as part of a thyroid blood test and it's 510 (140-724).

My previous test 10 weeks after 6 loading injections was 399 same range.

Then I had the first of my 12 weekly injections 6 weeks ago before this test and won't be getting my next one until 4th August.

I feel crap but my thyroid is still slightly out too.

Do you think I should be asking for more frequent?


10 Replies

Do you know whether your Folate level was tested Salphy as this works with B12 to help your iron produce red blood cells.

510 is not particularly high but if you are still having neurological symptoms it may be that you need more frequent injections


Hi Clive,

Yes folate >19.98 (2.91-50)

I'm on 5mg folic acid daily and guilty of forgetting it to take it.

Ferritin is 103.3 (13-150)

Iron wasnt checked this time but last time ferritin was 75 my iron was slightly high which my Dr called "healthy high"

Thanks :)

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Remember to take your supplement, leave the tab in the kitchen, next to a water jug or whatever, plus improve your diet with high folate foods (check online). Info I have from research is that it can take 3 to 4 months to recover from symptoms of low B12 so persistence is key, plus as others said improve B12 and folate/ iron. It is complex but do what you can for yourself.

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Thank you Geronimo. This is month 5 since starting injections :( I have taken my folic acid every day for the last week so I am trying to get in the habit. Need to get in the habit of vit d next. It would be so much easier if they could all be taken together! X


normal range doesn't really apply after loading shots as it introduces the possibility of functional deficiency because your serum levels have been high - what counts is whether you are still symptomatic - which is going to be difficult to gauge entirely because of the overlap with thyroid problems.

what is happening about sorting out your thyroid levels?


OK thanks Gambit.

Well I started 25mcgs in March, increased to 50mcgs 8 weeks later then this is my 8 week test following the increase so I have an appointment with my gp on Tuesday to hopefully increase a again. My TSH has come down from 6.53 on 25mcg to 4.7 (0.27-4.2) with the 50's so I'm not far off. My t3 hasn't increased that much though. 4.18 to 4.34.

It's really hard to know what's causing what but I'm getting the signs again, odd pins and needles more frequent but not for long, and blurred vision with one episode of double vision when I was really tired/stressed last week. As well as the usual fatigue, weight gain, dry skin etc x


it isn't uncommon for symptoms of B12 deficiency to seem to get a bit worse in the first 6 months or so of treatment - like nerves waking up after being asleep for a while - and the immune system coming back to life so reacting more to infections than in the past. Could be that if things are intermittent.

suggest you keep a diary of symptoms though as may be that frequency of injections isn't right for you and that should help to identify recurrence after a shot.

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Hi Gambit,

My thyroxine was increased again 11 days ago when my tsh was 4.7 (0.27-4.2) it came down from 6.53 to 4.7 with 50mcg and I'm now on 75mcg.

My b12 was 510 (140-724) 2 weeks ago and I'm feeling worse. Back at the point of napping daily.

I've got another 4 weeks until my next injection so really tempted to go it alone.

What's the treatment for functional deficiency?



you don't have functional deficiency (high serum but not enough getting through to cells). You may be being undertreated but its difficult to draw that conclusion at the moment.

Because of the overlap in symptoms it is difficult to know if your problem is the adjustments to thyroid or B12 - would really recommend that you make sure that your thyroid is under control before assuming it is B12 that is your issue.

Has the change in thyroxine had any effect?


No that's why I'm looking towards the b12 :( but worried about causing functional deficiency if I was to self inject.

I felt a bit better after the last injection but it was around the same time my thyroxine was increased from 25's to 50's. It lasted a few weeks then has been gradually getting worse since.

My thyroxine was increased again nearly 2 weeks ago but I haven't felt any change just continuing to gradually feel worse

Thanks again


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