Vitamin B12 (cobalamin)
Needed for nerves, DNA and red blood cells. It occurs naturally only in animal foods.
If you are short of it
Possible signs
- Tiredness, low energy
- Pale skin
- Tingling or numbness in hands and feet
- Poor memory or concentration
- Sore, red or smooth tongue
- Dizziness or poor balance
- Low mood or irritability
- Breathless on effort
These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.
Who is more at risk
Vegans and many vegetarians, adults over 50, people taking metformin or acid reducers long-term, weight-loss surgery, pernicious anaemia, Crohn’s or coeliac disease, breastfed babies of deficient mothers.
Foods rich in Vitamin B12 (cobalamin)
| Food | Serving | Amount | women 19–50 | men 19–50 |
|---|---|---|---|---|
| Beef liver | 85 g cooked | 70.7 NIH | 2946% | 2946% |
| Mackerel | 100 g cooked | 19 | 792% | 792% |
| Sardines (canned, with bones) | 1 can (90 g drained) | 8.2 | 342% | 342% |
| Salmon | 100 g cooked | 3 NIH | 125% | 125% |
| Beef (lean) | 100 g cooked | 2.6 NIH | 108% | 108% |
| Lamb | 100 g cooked | 2.6 | 108% | 108% |
| Tuna (canned, light) | 85 g, half a can | 2.5 NIH | 104% | 104% |
| Plain yogurt (low-fat) | 1 cup (245 g) | 1.4 NIH | 58% | 58% |
| Shrimp | 85 g cooked | 1.4 | 58% | 58% |
| Milk (fortified) | 1 cup (240 ml) | 1.3 NIH | 54% | 54% |
| Eggs | 2 large eggs | 1 NIH | 42% | 42% |
| Cod or other white fish | 100 g cooked | 1 | 42% | 42% |
| Fortified breakfast cereal | 1 bowl (30 g) — check the label | 0.6 NIH | 25% | 25% |
| Cheese (cheddar type) | 40 g, about 2 slices | 0.45 NIH | 19% | 19% |
Unit: mcg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.
As a supplement
Cyanocobalamin or methylcobalamin tablets, under-the-tongue forms, or injections when the problem is absorption (pernicious anaemia).
Too much
Very safe; excess is passed out. Nerve damage from long deficiency can become permanent — ask for a blood test (B12, sometimes MMA) rather than guessing.
How much you need each day
| Group | Recommended | Upper limit |
|---|---|---|
| Infants 0–6 months | 0.4 | — |
| Infants 7–12 months | 0.5 | — |
| Children 1–3 years | 0.9 | — |
| Children 4–8 years | 1.2 | — |
| Children 9–13 years | 1.8 | — |
| Boys 14–18 years | 2.4 | — |
| Girls 14–18 years | 2.4 | — |
| Men 19–30 years | 2.4 | — |
| Women 19–30 years | 2.4 | — |
| Men 31–50 years | 2.4 | — |
| Women 31–50 years | 2.4 | — |
| Men 51–70 years | 2.4 | — |
| Women 51–70 years | 2.4 | — |
| Men over 70 | 2.4 | — |
| Women over 70 | 2.4 | — |
| Pregnant 14–18 years | 2.6 | — |
| Pregnant 19–30 years | 2.6 | — |
| Pregnant 31–50 years | 2.6 | — |
| Breastfeeding 14–18 years | 2.8 | — |
| Breastfeeding 19–30 years | 2.8 | — |
| Breastfeeding 31–50 years | 2.8 | — |
Unit: mcg. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.
Interactions
Take care · Vitamin B9 (folate / folic acid)
High-dose folic acid can correct the anaemia of B12 deficiency while nerve damage goes on unnoticed. Check B12 when taking high-dose folic acid, especially if vegan or over 50.
Medicines and habits to mention to your doctor
Metformin (diabetes)
Long-term use can lower B12 absorption. Ask for a B12 check every year or two.
Acid reducers (omeprazole, esomeprazole, famotidine)
Long-term use lowers absorption of B12, iron, magnesium and calcium carbonate. Calcium citrate is a better choice; ask about monitoring.
Hormonal contraceptives
May lower B6, folate and B12 slightly. Usually minor with a normal diet; folic acid is still advised before a planned pregnancy.
Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)