Adenosylcobalamin B12 Capsules

Each capsule provides 1000 mcg of adenosylcobalamin, which is 40000% of the nutrient reference value. Take 1 capsule per day with food, as the label directs. A pot holds 90 capsules, a 90-day supply. The shell is vegetarian cellulose, and the capsules are vegan and free from gluten, dairy and nuts.

Sources: NIH Office of Dietary Supplements; product label.

Adenosylcobalamin, also called the mitochondrial form of B12, is one of the two forms of vitamin B12 that the body's enzymes use directly. Vitamin B12 is a family of compounds built around an atom of cobalt, which is why they are called cobalamins; the forms differ only in the small group attached to that cobalt. In adenosylcobalamin that group is an adenosyl group, and it is the form used inside the mitochondria by the enzyme that handles a step in the breakdown of fats and proteins for energy.

Sources: NIH Office of Dietary Supplements.

Adenosylcobalamin capsules give a fixed 1000 mcg a day in one step; the liquid gives 76 mcg per drop and builds up drop by drop. A capsule suits anyone whose amount is settled or has been set by a practitioner. The liquid suits anyone who wants to start low and adjust. NIH finds no difference in effect between the vitamin swallowed and the vitamin dissolved under the tongue, so neither route absorbs better.

Sources: NIH Office of Dietary Supplements; product label.

Capsules: a cellulose shell around the powder, so no coating is needed and it breaks down quickly once swallowed. Tablets need binders and a coating to hold their shape. These capsules contain adenosylcobalamin with cellulose as the carrier and nothing else.

Sources: NIH Office of Dietary Supplements; product label.

Adenosylcobalamin capsules suit anyone who wants the mitochondrial form on its own, often alongside methylcobalamin. Each active form serves a different enzyme: methylcobalamin works in the cell fluid with methionine synthase, which recycles homocysteine, and adenosylcobalamin works inside the mitochondria with the enzyme that processes certain fats and amino acids. The body converts between the two as needed, and NIH finds no evidence that absorption differs between the forms in supplements. No trial has shown one active form to outperform the other for general use. For the methylation form, see the methylcobalamin capsules; for all three forms in one bottle, see Tri-B12.

Sources: NIH Office of Dietary Supplements; NHS.

Adenosylcobalamin capsules are for people who want the form that works inside the mitochondria at a fixed daily amount. That includes anyone whose methylmalonic acid result came back raised and who wants the matching form with their GP's agreement, and vegetarians and vegans, who get little of the vitamin from diet. Food Standards Scotland names older adults, people who have had stomach or bowel surgery, and vegans and vegetarians as the groups most likely to run short. Anyone who thinks they may be low in B12 should ask a GP for a blood test rather than self-treating.

Sources: Food Standards Scotland; NIH Office of Dietary Supplements.

Adenosylcobalamin is most often taken with methylcobalamin, folate, iron or the other B vitamins, and no interaction with iron is listed by NIH. Folate and vitamin B12 work together on homocysteine. NIH flags one combination to avoid: a high intake of folic acid alongside low vitamin B12 has been associated with poorer mental function in older adults. Mayo Clinic advises leaving two hours or more between a vitamin C supplement and vitamin B12. Prescription drugs are the interactions that matter. Proton pump inhibitors and other acid reducers cut absorption of the vitamin from food, and metformin lowers blood levels, so anyone on regular prescriptions should ask a pharmacist first.

Sources: NIH Office of Dietary Supplements; Mayo Clinic.

Adenosylcobalamin raises the body's supply of vitamin B12 from the first dose, but the store it tops up is large. The body holds 1 to 5 mg of the vitamin, a thousand times or more the daily requirement, and a shortage takes years to develop. Absorption falls as the dose rises, which is why supplements carry far more than the daily requirement: about 2% of a 500 mcg dose is absorbed. In people who are short of the vitamin, a 2018 review of three trials found high doses by mouth restored blood levels. Anyone who started because of a low result should keep to the retest date a GP has set.

Sources: NIH Office of Dietary Supplements; NHS.

Adenosylcobalamin has no reported side effects at the amounts found in food or supplements. The body does not store the excess: what is not used passes out, which is why no safety ceiling has been needed. UK advice puts the level unlikely to cause harm at 2 mg a day from supplements. Observational studies have linked unusually high blood levels to poorer health outcomes, but trials giving supplements for two to seven years found little or no effect on serious illness or death rates. Anyone pregnant or breastfeeding, or taking prescribed tablets, should speak to a GP or pharmacist first.

Sources: NIH Office of Dietary Supplements; Food Standards Scotland.