Tri-B12 Methylcobalamin, Adenosylcobalamin and Hydroxocobalamin Drops

Tri-B12 is vitamin B12 supplied as three of its forms together: methylcobalamin, adenosylcobalamin and hydroxocobalamin. Vitamin B12 is the name for 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. Methylcobalamin and adenosylcobalamin are the two forms that the body's enzymes use directly, one for recycling homocysteine and one for a step in energy metabolism. Hydroxocobalamin is the form found in food and used for NHS injections, and the body converts it into whichever active form an enzyme needs. The fourth common form, cyanocobalamin, is not included.

Sources: NIH Office of Dietary Supplements; NHS.

Tri-B12 supplies vitamin B12, which the body needs to build red blood cells, to make DNA and to form and maintain the insulation around nerves. The vitamin works as a helper for two enzymes. One turns homocysteine, an amino acid, into methionine, which the body uses to supply methyl groups to DNA, proteins and fats; the other handles a step in the breakdown of fats and proteins for energy. Food Standards Scotland also lists releasing energy from food and processing folic acid among its jobs. Trials of extra vitamin B12 in people who are not short of it show little: supplements do not improve athletic performance or endurance, and in trials lasting up to two years they lowered homocysteine without improving memory or thinking. In people who are short of it, a 2018 review of three trials found high doses by mouth restored blood levels as well as injections did.

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

Tri-B12 and cyanocobalamin both supply vitamin B12, and the NIH finds no evidence that absorption differs between the forms of the vitamin in supplements. Cyanocobalamin is a single manufactured form that the body converts into the active forms; it is the most common form in tablets and fortified foods and the one used in most research. Tri-B12 combines the two active forms, methylcobalamin and adenosylcobalamin, with hydroxocobalamin, the form the NHS uses for injections because it is retained in the body for longer. Taking the active forms skips a conversion step, but that conversion works efficiently in most people, and no trial has shown a combination of forms to outperform a single form. Absorption, not form, is what limits how much of any supplement the body keeps.

Sources: NIH Office of Dietary Supplements; NHS.

Tri-B12 counts as vitamin B12, of which UK adults need about 1.5 mcg a day and American guidance sets 2.4 mcg. Supplement doses are far higher than that because absorption drops sharply as the dose rises: about half of a dose within 1 to 2 mcg is absorbed, but only about 2% of a 500 mcg dose and 1.3% of a 1000 mcg dose. Supplements containing vitamin B12 alone typically provide 500 to 1000 mcg for that reason, and trials that corrected a shortage by mouth used 1000 to 2000 mcg a day. No upper limit has been set, because the vitamin has little potential for harm, and UK advice is that 2 mg or less a day from supplements is unlikely to cause any harm. The groups most likely to run short are older adults, people who have had stomach or bowel surgery, and vegans and vegetarians.

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

Tri-B12 can be taken at any time of day, and the timing matters less for vitamin B12 than for most nutrients. The body holds a store of 1 to 5 mg, a thousand times or more the daily requirement, so a shortage takes years to develop and a missed day changes nothing. Vitamin B12 added to supplements is already in free form, so it does not need the stomach acid step that releases the vitamin from food, and NIH reports no difference in effect between tablets swallowed and tablets dissolved under the tongue. The NHS advises people taking vitamin B12 tablets for a diet-related shortage to take them every day between meals.

Sources: NIH Office of Dietary Supplements; NHS.

Tri-B12 is most often taken with folate, iron or the other B vitamins, and no interaction with iron is listed by the NIH. Folate and vitamin B12 work together on homocysteine, and trials that lowered it used the two side by side. 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, because vitamin C may reduce the amount of B12 available. 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. Anyone on regular prescriptions should ask a pharmacist first.

Sources: NIH Office of Dietary Supplements; Mayo Clinic.

Tri-B12 has no reported side effects at the doses found in food or supplements. The body does not store the excess vitamin B12: what is not used passes out, which is why even large doses are considered safe and why no safety ceiling has been needed. Observational studies have linked unusually high blood levels of the vitamin to poorer health outcomes, but trials giving supplements for two to seven years found little or no effect on serious illness or death rates, so the link is not thought to be caused by the supplements. UK advice puts the level unlikely to cause harm at 2 mg a day from supplements. Anyone pregnant or breastfeeding should speak to a GP or pharmacist first.

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

Tri-B12 does not occur in food as such; the vitamin B12 in food is found only in foods of animal origin. Meat, fish, poultry, eggs and dairy foods all contain it, and liver, clams and oysters hold far more per serving than anything else. Salmon, tuna, beef, milk, yoghurt, cheese and eggs are the everyday sources. Plant foods contain none, so vegans rely on fortified foods: yeast extract, fortified breakfast cereals, fortified soya products and nutritional yeast, which the NIH lists as well absorbed. Absorption from dairy appears to be about three times higher than from meat and fish, and absorption from supplements is about half as high again as from food.

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