Vitamin B12 Intake Calculator
Vitamin B12 (cobalamin) is an essential nutrient required for red blood cell formation, neurological function, and DNA synthesis. Because it is found almost exclusively in animal-derived foods, vegans and vegetarians face a significantly higher risk of deficiency. The recommended dietary allowance (RDA) varies by life stage: adults need 2.4 micrograms (mcg) per day, rising to 2.6 mcg during pregnancy and 2.8 mcg while breastfeeding. Older adults often require higher intakes through fortified foods or supplements because gastric acid production declines with age, reducing absorption of naturally occurring B12. This calculator shows the NIH RDA for your age, sex, and dietary pattern, plus guidance on whether supplementation is recommended.
Vitamin B12 RDA by life stage (NIH ODS)
RDA (mcg/day): 0-6 mo: 0.4 (AI); 7-12 mo: 0.5 (AI); 1-3 yr: 0.9;
4-8 yr: 1.2; 9-13 yr: 1.8; 14+ yr: 2.4; Pregnant: 2.6; Lactating: 2.8
No tolerable upper limit (UL) established. No adverse effects from high doses.
Vitamin B12: frequently asked questions
How much vitamin B12 do I need daily?
The NIH recommends: infants 0-6 months: 0.4 mcg/day; infants 7-12 months: 0.5 mcg/day; children 1-3 years: 0.9 mcg/day; children 4-8 years: 1.2 mcg/day; children 9-13 years: 1.8 mcg/day; teens 14+ and adults: 2.4 mcg/day; pregnant women: 2.6 mcg/day; breastfeeding women: 2.8 mcg/day.
Who is at risk of vitamin B12 deficiency?
Groups at high risk include vegans and vegetarians (B12 is found almost exclusively in animal products), older adults (reduced gastric acid impairs B12 absorption), people who have had gastric surgery or take metformin long-term, and those with pernicious anemia or other malabsorption conditions. Deficiency causes fatigue, anaemia, and neurological damage.
What foods are highest in vitamin B12?
Clams and oysters are the richest sources, providing over 80 mcg per 3 oz. Beef liver provides 70 mcg per 3 oz. Fish (trout, salmon, tuna) provide 2-9 mcg per serving. Beef, dairy products, and eggs provide 0.5-2.5 mcg per serving. Fortified cereals and plant milks provide varying amounts and are the main sources for vegetarians.
Is there a safe upper limit for vitamin B12?
No tolerable upper intake level (UL) has been set for vitamin B12 because no adverse effects have been associated with excess intake from food or supplements in healthy people. The body absorbs only a small fraction of very high doses, and excess is excreted in the urine. Very high supplemental doses should still be discussed with a healthcare provider.
Do vegans need to supplement vitamin B12?
Yes. The NIH strongly recommends that vegans and most vegetarians supplement vitamin B12 or eat B12-fortified foods daily. Plant foods do not contain reliable amounts of active B12. Deficiency can develop slowly over years and cause irreversible neurological damage before symptoms are obvious. Regular blood testing is recommended for people following plant-based diets.
Official sources
- NIH Office of Dietary Supplements: Vitamin B12 - Health Professional Fact Sheet.
- National Academy of Medicine: Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12.
Reviewed by the CalculatorHub team, edited by James Graham, 14 June 2026. See our methodology.