C and Vitamin B12 — Sabotaging Absorption
High doses of vitamin C (often used for immune support) can interfere with the absorption of vitamin B12 in the digestive tract, especially when taken together in large quantities. Vitamin C can chemically alter B12, reducing its bioavailability. In older adults—who already experience lower stomach acid and a higher risk of B12 deficiency—this combination can worsen fatigue, tingling, or brain fog.
Quick Tip: Separate the doses by at least 2 hours. Take B12 in the morning on an empty stomach and reserve vitamin C
Seniors: 7 Supplement Combinations You Should Never Take Together (And Safer Alternatives)
