Metformin reduces ileal absorption of B12 by competing with the calcium-dependent intrinsic factor-B12 receptor. Up to 30% of long-term users become clinically deficient.
Ting et al. (2006) NEJM — 30% B12 deficiency rate in metformin users over 4 years; ADA guidelines recommend annual B12 monitoring
Peripheral neuropathy, cognitive decline, fatigue, anemia, elevated homocysteine
Methylcobalamin 1,000–2,000mcg daily (sublingual preferred — bypasses gut absorption issue). Test serum B12 and homocysteine annually.
View on Fullscript: Thorne Methylcobalamin 1mgDiscuss with your physician before adjusting supplementation. This is educational content, not medical advice.
Metformin reduces folate absorption via similar mechanisms to B12. Compounded in individuals with MTHFR gene variants (40% of the population).
Sahin et al. (2007) — significantly lower folate levels in metformin vs. non-metformin diabetic patients
Elevated homocysteine (cardiovascular risk), fatigue, mood disturbance
L-Methylfolate 400–800mcg daily. Use methylfolate, not folic acid — 40% of people cannot convert folic acid.
View on Fullscript: Thorne 5-MTHF (Methylfolate)Discuss with your physician before adjusting supplementation. This is educational content, not medical advice.
Metformin inhibits mitochondrial Complex I, reducing cellular energy demand for CoQ10 — but also impairing mitochondrial function as a side effect.
Murtha et al. (2018) — measurable reduction in mitochondrial CoQ10 in long-term metformin users
Fatigue, reduced exercise capacity, muscle weakness
Ubiquinol 100–200mg daily with meals.
View on Fullscript: Jarrow QH-Absorb Ubiquinol 100mgDiscuss with your physician before adjusting supplementation. This is educational content, not medical advice.
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