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Pernicious Anaemia Society
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Brain fog not going even after 6 weeks of b12 supplements. Help

I was diagnosed with b12 deficiency 6 weeks back. My B12 was 144 Pg/ml. Doctor gave 1500mcg sublinguals and 5 injections every 5 days of 500 mcg. I went to doctor and he told me to do test again. This time it was 1767 Pg/ml. He is not sure why my brain fog is not going. He told me stop supplements for 2 weeks and start again and gave me Xanax for relief. What shud I do?

5 Replies

Hi HD12

It is not uncommon for some symptoms to appear to get worse before they get better as the B12 starts repairing the damage done to your nervous system and your brain starts getting multiple messages from part of the body it had "forgotten about" or lost contact with.

I sometimes liken it to a badly tuned radio on which you have turned the volume up high trying to catch the programme you want when all of a sudden the signal comes in loud and clear and the blast nearly deafens you.

A lot will depend on the severity and longevity of your B12 deficiency as to how long before there is no further improvement or recovery. Some symptoms will "disappear" quite quickly whereas others may take months or even years. There is no set timescale as we are all different.

It is also important that your Folate level is monitored as this is essential to process the B12.

There is a complex interaction between folic acid, vitamin B12 and iron. A deficiency of one may be "masked" by excess of another so the three must always be in balance.

Symptoms of a folate deficiency can include:

symptoms related to anaemia

reduced sense of taste


numbness and tingling in the feet and hands

muscle weakness


Folic acid works closely with vitamin B12 in making red blood cells and helps iron function properly in the body.

I am not a medically trained person but have had P.A. (a form of B12 deficiency) for more than 45 years

1 like

levels after you have had loading doses really don't mean a lot unless they come back low - normal range really doesn't apply (possibility of functional deficiency)

functional deficiency most likely caused by a reaction to raised serum levels which means B12 doesn't move from blood to cells leaving you deficient at the cell level - most effective treatment is probably keeping levels of B12 so high that enough manages to get through to cells.

In theory raised MMA and homocysteine would be markers.

Have you kept a diary of symptoms? that you could review with doctor to see if there has been a pattern of improvement with injections then a rapid decline?


Hello , I was also experiencing horrible brain fog with lots of other side effects.. and my doctor could never really diagnose me. She kept saying I had an ear infection. Or that my anxiety was the cause... and provided Xanx ! Which I would take them every day and it just seemed to worsen my brain fog and anxiety. Where at times I felt like something horrible was going to happen too me and felt useless. I was finally recommended to a Neurologist where he asked me a million questions and did several little exams on me. He came to the conclusion that I suffer from Aurora Migraines which is like a silent migraine because there is no pain it just gives you the brain fog , spots in your vision, anxiety! And many other symptoms. Which we may not all experience the symptoms but brain fog is one! I was recommended B12 and Magnesium and BAMM I am myself again. I've been experiencing brain fog since I was 16 and I am now 22 and loving life. Please see a neurologist!


Thanx for your reply :) But I am already taking b12 supplements. Can you tell me how much time it took for you for brain fog to go ?


You have to take b12 and magnesium together. It took two weeks for it to be effective.


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