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Pernicious Anaemia Society
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First B12 injection!

Hi guys, I've previously told you about a friend of mine who suffers from PA. I've also been suffering many of the symptoms myself too. I have read so many stories about late diagnoses and it scares me so I decided to go private and get a blood test done for intrinsic factors. The thing is I've been feeling soo unwell and in a lot of pain for the last 2 days so I decided to take a B12 injection asap to see if it helps.

When will I see the Benifits of the shot? And how long will the B12 stay in my blood. I need to know this in order to get the private test done whenever I can.

Appreciate all comments.

6 Replies

How long is a piece of string?

It depends on several factors. Some people find almost instant relief from some symptoms. Others find that some symptoms get worse with the first injections. Others find there's little change for a long time. I would say that most people don't find instant relief from one injection.

The modern anti-IF test doesn't get interference with B12. The older test needs a few days after a jab (the even older test needs a long time - but I doubt anybody still uses that). A week should be long enough.


Please make sure that you have someone with you for the first injection - ideally someone with medical qualifications.

It is extremely rare but some people do have allergic reactions and the first shot would be the point at which this manifests.


I did thank you. I had it last night and not long got up 😖 I feel a surge of energy and no pain! Feels so good I hope it lasts a while. Thank god I haven't had any allergic reactions aside from a tiny bruise on site of the injection. I can live with that.

Thanks gambit62 :)


Each person is different and exhibits different symptoms to different degrees of severity.

Start your own logbook and treat each jab as day zero and count from there. Assess each symptom with your own severity score, record new symptoms as you notice them.

There are some new symptoms that will appear and repeat within 72 hours of the jab. These are similar to other symptoms from the deficiency.

Get to know your body.

Stress consumes B12.

Food and drink issues can also cause similar symptoms and mask or confuse your analysis so record your food, drink and medication. There is usually a 3 to 48 hour lag in these symptoms because the gut and liver are involved.


Thank you /pvanderaa,

That is a really good idea I didn't think of that. I will start to keep a log and make notes on everything so I can read back. This will especially be helpful as my short term memory has become awful. Thank you again for your response it's really helpful :)

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I'm not clear if you've had the private b12 test before you had an injection of B12.

Supplementing with B12 prior to tests can affect the results of tests for B12 deficiency.


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