Vitamin B12 Supplements: Who Needs It, How Much & What to Buy

Vegetarian? Eggs and milk may not cover you.

Vegetarians run low on B12 more often than meat eaters (NIH). If your level is normal, this 100 mcg tablet keeps it there. It will not fix a low level.

Carlyle Vitamin B12 100 mcg
$0.04 a day, labeled vegan

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Vegan? Many B12 pills contain gelatin.

This lemon chewable holds 1,000 mcg and is labeled vegan. Our pick’s softgel uses gelatin. B12 for vegans and vegetarians.

Jarrow Methyl B-12 1000 mcg
$0.13 a day

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Who needs a B12 supplement

• Adults over 50. Many absorb the B12 in food poorly, so the Institute of Medicine advises getting most of it from a pill or fortified food. B12 for seniors.
• Vegans and many vegetarians. Only animal foods and fortified foods have B12 (NIH).
• People on metformin or acid reducers. Metformin can lower B12 over time (de Jager 2010). Years of acid reducers are linked to low B12 (Lam 2013).
• People with pernicious anemia, celiac disease or past stomach surgery. See pills or shots.

Eat meat, fish, eggs or dairy and fit none of these? Then food likely covers you.

How much B12 a day, and why pills hold so much

The 2.4 mcg rises to 2.6 mcg in pregnancy and 2.8 mcg while breastfeeding, and it does not go up with age (NIH). Pills hold far more because you absorb only about 13 mcg of a 1,000 mcg pill (NIH). About 1 in 3 of the 203 B12 labels we read hold exactly 1,000 mcg. B12 dosage guide, with the chart for every age.

Signs you may be low on B12

Tiredness, weakness, pale skin, a sore tongue, and numbness or tingling in the hands and feet are common signs. Memory problems can come later (NIH). Signs can take years to show. All the signs of B12 deficiency.

A “normal” B12 test can still miss a deficiency

A blood B12 under 200 to 250 pg/mL is usually called low (NIH). If yours is near that line and you have symptoms, ask about a methylmalonic acid (MMA) test, the most sensitive check (NIH). The MMA test explained.

Methylcobalamin or cyanocobalamin?

Either works for most people. NIH says the body absorbs both forms the same. So choose by testing and price. Kidney disease: ask your doctor which form and dose of B12 to take. Methylcobalamin vs cyanocobalamin.

Pills or shots?

A daily pill is enough for most people. Small trials found big-dose pills raised blood B12 about as well as shots (Wang 2018). Pernicious anemia and nerve symptoms are usually treated with shots (NIH). After stomach or weight-loss surgery, follow your surgical team’s B12 plan. How low B12 is treated.

B12 helps only if you are low

B12 keeps your blood and nerves healthy, and treating a real shortage helps (NIH). If your level is normal, more B12 has not been shown to add energy (Markun 2021). In trials, B vitamins did not prevent heart attacks or improve memory in older adults (NIH). B12 for energy and fatigue.

How long B12 takes to work

Blood B12 rose within 4 weeks on 500 mcg a day in people who were low (Sharabi 2003). In a trial in older adults, most were back to a normal level within 8 weeks (Sanz-Cuesta 2020). Ask your doctor when to retest. If a blood test says you are low.

Is 1,000 mcg too much? Side effects

No upper limit has been set for B12 (NIH). Side effects are rare at supplement doses, though a few people get an acne-like rash that clears after stopping (Veraldi 2018). Ask a doctor first if you have a cobalt allergy (FDA label) or take high-dose folic acid, which can hide low B12 (Miller 2024). Men who smoke should ask before taking high doses for years (Brasky 2017). Who should be careful with high doses.

Which B12 to buy

NatureWise, our pick, is above. If you want methylcobalamin, this one is on a public testing list, so an outside lab has checked what is inside.

Thorne Vitamin B12 (methylcobalamin)
$0.40 a day. Methylcobalamin, tested by NSF. The priciest of the tested pills.

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If your doctor wants a higher dose: NOW Methyl B-12 5000 mcg or Solgar Methylcobalamin 5000 mcg lozenges.

Prices are each brand’s own list price. Amazon’s price can differ. The best B12 supplements, ranked.