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Pernicious Anaemia Society
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Antibiotics (Erythromycin) and B12

I was feeling unwell 2 weeks before my last B12 jab, so much so I snuck in a week early without being queried this time. However I didn’t notice the usual post injection improvement. 2 weeks later I was back as the GP feeling even more unwell. I am now on the antibiotic Erythromycin.

Anyone know what impact this antibiotic may have on B12 levels. Has my injection been wasted and is it worth using sublinguals whilst on antibiotics or better to wait till I have finished the course.

Crawling back under the duvet now.

3 Replies

I think the effect antibiotics have on B12 is the what they have on your stomach acid levels so if you are having B12 injected it shouldn't be a concern.

However, I'm not medically trained so hopefully there will be a "night owl" on here who can be more authoritative.

I hope you feel better soon. Goodnight


From the B12 deficiency survival handbook by Dr Aqsa Ghazanfar and Regev Elya

Some antibiotics interact with B12 by decreasing its ability to make up new red blood cells, provided that both the antibiotic and B12 are given together. This does not mean that anyone who has an infection will develop a B12 deficiency if he or she is given one of these antibiotics, it only applies to those people who are already deficient in B12. In simple terms, anyone who is being given B12 for the treatment of a deficiency should nto be given certain antibiotics (those belonging to the amino-glycoside group, such as gentamicin, tobramycin, etc) because these decrease the efficacy of B12.

Unfortunately there isn't an obvious supporting reference for the statement above in the book.

This is a link to a list of relevant antibiotics - it doesn't include erythromycin which at it is a macrolide antibiotic.



Thanks clivealive and Gambit62 . I think the cure is worse than the disease at the moment as I feel worse than before the antibiotics. Only another 3 days of hell to go, hope it is worth it and when the dust eventually clears I will feel better.


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