HealthRX.com · Printable lab tracker
Vitamin B12 with NMN or NR: metformin and B12 lab tracker
Tick the B12 risk factors this page lists, write down your metformin, acid-reducer, B12 and NMN or NR doses, and keep serum B12, methylmalonic acid, homocysteine and blood count results with any numbness or tingling in one place for your next review.
B12 risk factors this page lists
- Taking metformin (note the years and daily dose below)
- Age 60 or older
- Vegan or strict vegetarian diet
- Long-term proton pump inhibitor or H2 blocker
- Numbness, tingling or anemia already noted
- Leber's hereditary optic neuropathy (ask about the B12 form)
What you take
Metformin: mg a day and years taken
Acid reducer and how longomeprazole, pantoprazole, famotidine
Vitamin B12: form and mcg a daycyanocobalamin, methylcobalamin, sublingual or injection
NMN or NR product and mg a day
What the metformin label and the studies state
- The metformin label says it may lower vitamin B12, and asks for blood counts every year and B12 at 2 to 3 year intervals.[1]
- In 29-week metformin trials, about 7% of patients with previously normal B12 fell to subnormal levels.[1]
- In US adults 50 and older, 5.8% of metformin users with diabetes had biochemical B12 deficiency, compared with 2.4% of people with diabetes not on metformin.[2]
- A 2 years' or longer supply of a PPI was associated with higher odds of B12 deficiency (odds ratio 1.65); for H2 blockers, 1.25.[3]
B12-related lab results
| Test | Date | Result | Reference range | Notes |
|---|---|---|---|---|
| Serum vitamin B12 | ||||
| Methylmalonic acid (MMA) | ||||
| Homocysteine | ||||
| Blood count (hemoglobin, MCV) |
Nerve and energy symptoms
| Date | Numbness or tingling (where) | Fatigue or brain fog | Other changes |
|---|---|---|---|
Questions for your clinician
- Given how long I have taken metformin, is a B12 check due now?
- If my B12 is borderline, should methylmalonic acid be tested as well?
- Which B12 form and dose suit me, and when do we recheck?
- Could my numbness or fatigue be B12-related rather than from my other treatments?
Sources for the facts on this sheet
- Zydus Pharmaceuticals USA, via DailyMed. Metformin hydrochloride tablets, for oral use: prescribing information and patient information. Effective 2026-07-15. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=c82a10fa-1e8e-46b6-890a-737de3f34ee1
- Reinstatler L, Qi YP, Williamson RS, et al. Association of biochemical B₁₂ deficiency with metformin therapy and vitamin B₁₂ supplements: the National Health and Nutrition Examination Survey, 1999-2006. Diabetes Care 2012. PMID 22179958. https://pubmed.ncbi.nlm.nih.gov/22179958/
- Lam JR, Schneider JL, Zhao W, et al. Proton pump inhibitor and histamine 2 receptor antagonist use and vitamin B12 deficiency. JAMA 2013. PMID 24327038. https://pubmed.ncbi.nlm.nih.gov/24327038/
This sheet records information for a conversation with your prescriber or pharmacist. It does not replace their instructions or the medication's prescribing information.