Daily vitamin B12 intake for most healthy adults is around 2.4 micrograms from food and supplements combined.

Most adult women need about 2.4 micrograms of vitamin B12 a day, rising to around 2.6–2.8 micrograms during pregnancy and breastfeeding.

Most healthy vegans do well with a vitamin B12 supplement of 25–100 mcg daily or 1000–2000 mcg once or twice a week from a reliable product.

Most older women do well with about 2.4 micrograms of vitamin B12 a day, often from a mix of food and a small daily supplement.

Most adults with diabetes aim for 2.4 mcg of vitamin B12 daily, with 25–100 mcg supplements used if diet or medicines lower levels.

Most healthy adult women need about 2.4 micrograms of vitamin B12 per day, with slightly higher amounts during pregnancy and breastfeeding.

Most adults on metformin often take 500–1000 micrograms of vitamin B12 daily, set after blood tests and a shared plan with their doctor.

Most healthy adult men only need about 2.4 micrograms of vitamin B12 a day, usually met through a mixed diet or a modest supplement.

Most healthy adults need about 0.0024 mg (2.4 mcg) of vitamin B12 per day, with slightly higher amounts during pregnancy and breastfeeding.

Healthy adults need about 2.4–2.8 mcg of vitamin B12 per day, and up to 2 mg daily from supplements appears safe for long-term use.