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Vitamin

Vitamin B12

Content pending expert reviewSources checked 9 Oct 2026

This article is written from cited public sources but has not yet been signed off by a qualified expert. Use it as general background only, and check important details with a health professional.

Vitamin B12 keeps nerves and blood cells healthy. It is found naturally only in animal foods, so people who eat little or no milk, curd, eggs, fish or meat need to plan for it.

What is Vitamin B12?

Vitamin B12 (cobalamin) is a water-soluble vitamin found naturally in animal foods and added to some fortified foods.[1]

To absorb B12 from food, the body needs stomach acid and a protein made in the stomach called intrinsic factor.[1]

Its role in the body

  • Needed to make healthy red blood cells.[1]
  • Needed for the brain and nerves to work properly.[1]
  • Helps the body make DNA, the genetic material in every cell.[1]

Important food sources

  • Milk, curd (dahi), buttermilk and paneerImportant sources for Indian vegetarians.
  • Eggs
  • Fish and shellfish
  • Chicken, mutton and liverLiver is especially rich.
  • Fortified foodsSome breakfast cereals and plant milks are fortified; check the label.
  • Plant foodsPlant foods such as dal, vegetables and grains do not naturally provide reliable B12.

Recommended dietary intake

General population reference values, not personal targets.
GroupAmountBasisRegion
Adult men (Indian reference)ICMR-NIN 2020 value for the reference Indian adult (men 65 kg, women 55 kg). ICMR-NIN recommends using the EAR for planning diets.2.2 mcg/day[2]RDAIndia
Adult women (Indian reference)ICMR-NIN 2020 value for the reference Indian adult (men 65 kg, women 55 kg). ICMR-NIN recommends using the EAR for planning diets.2.2 mcg/day[2]RDAIndia
Adult men and women (Indian reference)2 mcg/day[2]EARIndia
Adults 19+ years2.4 mcg/day[1]RDAUSA
PregnancyUS value; Indian reference value to be added after verification.2.6 mcg/day[1]RDAUSA
BreastfeedingUS value; Indian reference value to be added after verification.2.8 mcg/day[1]RDAUSA

Signs sometimes associated with low levels

  • Tiredness and weakness, which can come with a type of anaemia (megaloblastic anaemia).[1]
  • Nerve changes such as numbness or tingling in the hands and feet, balance problems, memory trouble or mood changes.[1]
  • A sore, smooth tongue (glossitis) or a feeling of the heart racing (palpitations).[1]
  • Signs can take several years to appear because the body stores B12.[1]

Why symptoms alone cannot confirm a deficiency

Signs like tiredness, weakness, hair fall or low mood are very common and have many possible causes, such as poor sleep, stress, infections, thyroid problems or other illnesses.

The same sign can come from several different nutrients, or from no nutrient problem at all.

Only a qualified clinician, using your history, an examination and, when needed, lab tests, can say whether a deficiency is present. This app cannot diagnose a deficiency from symptoms or from BMI.

Low folate can cause the same type of anaemia as low B12, and nerve symptoms have many other causes, so tests are needed to tell them apart.

Tests a clinician might consider

  • Blood vitamin B12 level.[1]
  • Methylmalonic acid (MMA), the most sensitive marker of B12 status, often used when the B12 level is borderline. Homocysteine may also be checked.[1]
  • A complete blood count to look for anaemia. Tests for the cause, such as for pernicious anaemia, may follow.[1]

Who is more likely to have low intake

  • People who follow vegetarian or vegan diets, especially those who eat little dairy or eggs.[1]
  • Babies of mothers who follow vegan diets.[1]
  • Older adults, many of whom absorb B12 from food less well.[1]
  • People with pernicious anaemia, stomach or bowel conditions (such as celiac disease or Crohn’s disease), or who have had stomach or bowel surgery, including weight-loss surgery.[1]
  • People who take certain medicines for a long time, such as metformin or acid-reducing medicines.[1]

Potential benefits and quality of evidence

  • Adequate B12 is essential for healthy blood cells and nerves; correcting a diagnosed deficiency treats its anaemia and can stop nerve damage from getting worse.[1] Established
  • B12 supplements have not been shown to lower the risk of heart disease.[1] Not enough evidence
  • Trials have not shown that B12 supplements improve memory or thinking in older adults with or without dementia.[1] Not enough evidence
  • B12 supplements do not appear to boost energy or sports performance in people who already have enough.[1] Not enough evidence

Side effects

  • No harmful effects have been linked to B12 from food or supplements in healthy people.[1]

Risks of too much

  • No upper limit has been set because B12 has low potential for harm, even at high intakes. This does not mean that unneeded high-dose products are useful.[1]
  • Some studies have reported links between high B12 intakes or blood levels and cancer, while others have not; the research is unclear.[1]

Medicine and supplement interactions

  • Acid-reducing medicines (proton pump inhibitors such as omeprazole, and H2 blockers): Long-term use can reduce absorption of B12 from food.[1]
  • Metformin (diabetes medicine): Long-term use may lower B12 levels.[1]

Never start, stop or change a prescribed medicine because of this list — talk to your doctor or pharmacist.

Pregnancy and breastfeeding

  • Needs are slightly higher in pregnancy and breastfeeding. Babies of mothers with low B12, especially mothers on vegan diets, can develop deficiency, so B12 is worth discussing at antenatal visits.[1]

Kidney and liver cautions

  • No specific kidney or liver limits are given for B12 from food. People with kidney or liver disease should check with their doctor before using any supplement, as their care team may monitor blood tests.[1]

Upper intake limits

The US Food and Nutrition Board did not set a Tolerable Upper Intake Level for vitamin B12 because of its low potential for toxicity.[1]

When to talk to a professional

Talk to a doctor or registered dietitian before starting a supplement, especially if you are pregnant or breastfeeding, have a long-term illness, or take any regular medicines.

Do not start, stop or change a prescribed medicine because of anything you read here.

Supplements sold without a prescription are not automatically safe. Doses, quality and interactions still matter.

Seek medical care promptly if you have severe, sudden or worsening symptoms.

If you follow a vegetarian or vegan diet, ask a doctor or dietitian how to meet your B12 needs.

Numbness, tingling, balance problems or memory changes should be checked by a doctor rather than self-treated.

Still being verified

  • ICMR-NIN 2020 values for pregnancy/lactation not verified; not stated.

References

  1. NIH Office of Dietary Supplements. Vitamin B12 — Fact Sheet for Health Professionals (opens in a new tab) (2025-07-02). Accessed 9 Oct 2026.
  2. ICMR-National Institute of Nutrition (India). A Brief Note on Nutrient Requirements for Indians, the Recommended Dietary Allowances (RDA) and the Estimated Average Requirements (EAR), ICMR-NIN, 2020 (opens in a new tab). Accessed 9 Oct 2026.

Sources checked: 9 Oct 2026

This page is general education, not personal medical advice. For diagnosis, treatment or medicines, please talk to a qualified doctor, registered dietitian or pharmacist. Read our medical & AI disclaimer.