Can you take Vitamin B12 (Cobalamin) with Folate (Vitamin B9)?

These two work on the same pathway, and taking folate without knowing your B12 status is the one combination worth thinking about carefully. Folate and B12 both feed the conversion of homocysteine to methionine, and a shortage of either produces the same macrocytic anaemia. Folic acid can correct that anaemia on its own — which sounds like a good thing, and is the problem. The anaemia is the visible warning sign of B12 deficiency; the damage that matters is neurological, and it continues underneath while the blood count looks normal. In an analysis of 1,459 older Americans after folic acid fortification began, people with low B12 who also had high serum folate had roughly three times the odds of anaemia and 2.6 times the odds of cognitive impairment compared with those with low folate, while in people whose B12 was normal high folate was, if anything, protective. The harm is specific to the pairing of high folate with low B12, not to folate itself. Taking the two together is therefore the sensible arrangement rather than a risky one, which is why this is marked supportive: adequate B12 removes the thing that makes high folate a problem. Two caveats worth carrying. A supplement is not a test — if you have a reason to suspect low B12, such as a vegan diet, being over 60, or long-term metformin or acid-suppressing medication, ask for it to be measured rather than assuming a combined tablet has covered it. And the evidence is genuinely contested: a 2024 review judges the masking concern compelling enough to warrant vigilance while noting it rests largely on correlational data, and other authors argue it is overstated. The practical advice is the same either way.

[1], [2]