There has long been discussion about whether it is acceptable to commence treatment with Folic Acid (or any other folate) in those who are deficient in vitamin B12.
In many cases, it seems quite reasonable to take the precautionary approach of commencing B12 (whether orally or by injection) before any Folic Acid. Especially as, so long as the B12 level does rise, that seems sufficient to avoid any possible problems.
However, the underlying issues are important.
"Regarding dose-response, it is also noteworthy that >95% of the 155 cases in which folic acid supplementation was reported to precipitate neurologic manifestations occurred before 1963, during which time the FDA recommended dosage was 5–20 mg folic acid/d"
from
Knowledge gaps in understanding the metabolic and clinical effects of excess folates/folic acid: a summary, and perspectives, from an NIH workshop
https://www.sciencedirect.com/science/article/pii/S0002916522009091
There are several papers suggesting (but not proving certainly), that high dose folic acid in low b12 states may further impair B12 status. For all these reasons there are many questions about the 5mg daily folic acid ideas that float around. Most especially, the idea that such a large dose is absolutely essential in all who receive B12 injections.
In general, doctors seem to expect patients to buy their own for low dose supplementation (doses lower than 500 micrograms may be sold directly to the public). Or they prescribe 5mg which is prescription-only. If the doctor is involved at all, they tend to prescribe 5mg to everyone.
Folate dietary insufficiency and folic acid supplementation similarly impair metabolism and compromise hematopoiesis
https://www.haematologica.org/article/view/8276
Excessive Folic Acid Mimics Folate Deficiency in Human Lymphocytes
https://www.mdpi.com/1467-3045/44/4/97
Perspective: The High-Folate-Low-Vitamin B-12 Interaction Is a Novel Cause of Vitamin B-12 Depletion with a Specific Etiology-A Hypothesis
https://pubmed.ncbi.nlm.nih.gov/34634124/
For more information about B12 (and folate), it is suggested you visit the Pernicious Anaemia Society forum on HealthUnlocked. Specifically look for the Pinned Posts and consider joining the forum and the Society itself:
https://healthunlocked.com/pasoc/
USA National Institutes of Health: Office of Dietary Supplements
Papers about folate (folic acid) and vitamin B12 which have a lot of detail especially in relation to requirements and dietary availability. Though do be careful as some aspects are specifically related to the USA.
Folate
https://ods.od.nih.gov/factsheets/Folate-HealthProfessional/
Vitamin B12
https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
If you wish to link to this page on HealthUnlocked, copy the entire dark red text below and paste into a post or reply.
[i][b]helvella - Folate/Folic Acid and B12 Deficiency[/b]
A short discussion about commencing folate/folic acid supplementation in those who have low levels of vitamin B12.
Last updated 10/02./2025[/i]
Link to blog:
https://helvella.blogspot.com/p/helvella-folatefolic-acid-and-b12.html
If you find anything incorrect, misleading, typos, links that don’t work, etc., please let me know. Go to my profile and use the contact details there.
