Vitamin B12

Several studies have shown low levels of vitamin B12 in HIV-positive people.1,2 It is unclear whether low vitamin B12 levels influence HIV disease progression, or whether they are merely a consequence of disease progression. An 18 month study of HIV-positive people found that the onset of low serum vitamin B12 levels was associated with CD4 cell count decline, and that normalisation of vitamin B12 levels was associated with an improvement in CD4 cell count.3 Another study, which followed 310 men for 9 years, found that low serum vitamin B12 levels at entry to the study were associated with an 89% increased risk of progression for AIDS after controlling for disease stage, antiretroviral therapy, alcohol intake and age.4

Depletion in body tissues may begin to occur at least a year before blood levels become abnormally low. Vitamin B12 is thought by some doctors to protect against nerve damage and neurological disorders.

Injected supplementation has been tested in HIV-positive people and appears to improve mental functioning.5 Another study also showed that vitamin B12 supplementation for at least six months improved mental functioning in HIV-positive people who had been deficient; an untreated control group did not show improvement.3

Peripheral neuropathy, a symptom sometimes seen in HIV-positive people and often related to the use of drugs such as ddI (didanosine, Videx / VidexEC) and ddC (zalcitabine, Hivid), can be caused by vitamin B12 deficiency, so this should always be ruled out before assuming that the neuropathy is HIV-related. As yet there is no evidence that prophylactic treatment with vitamin B12 will reduce the likelihood that neuropathy will develop in those receiving ddI or ddC.

It has been suggested that vitamin B12 supplementation may reduce the risk of neutropenia and anaemia resulting from AZT (zidovudine, Retrovir) use. Vitamin B12 is used in the production of thymidine phosphate, necessary both to break down AZT in the blood and to create red blood cells. Unless enough of this vitamin is present, AZT competes with red blood cells for available thymidine triphosphate. People who are already deficient in vitamin B12 when they begin AZT therapy may be more vulnerable to anaemia and neutropenia.6 However, one study showed that vitamin B12 supplementation does not reduce AZT toxicities once therapy has begun.7

Absorption of vitamin B12 in HIV-positive people with gastrointestinal problems is poor unless the vitamin is injected or taken in a form that will dissolve in the mouth and be absorbed across the mucous membranes, according to some nutritionists. This vitamin treatment is available on National Health Service prescription for dietary deficiency.

All the B vitamins operate in combination, and also act in conjunction with other vitamins and minerals, so vitamin B12 is best taken alongside a B-complex formula. Good food sources are fish, dairy products, kidneys, liver, eggs, beef and pork. Vegans' diets are especially likely to lack vitamin B12.8

Vitamin B12 is also known as cobalamin.


  1. Burkes RL et al. Low serum cobalamin levels occur frequently in the acquired immune deficiency syndrome and related disorders. Eur J Haem 38: 141-147, 1987
  2. Harriman GR et al. Vitamin B-12 malabsorption in patients with acquired immune deficiency syndrome. Annals of Internal Medicine 149(9):2039-2041, 1989
  3. Baum MK et al. Micronutrients and HIV-1 disease progression. AIDS 9: 1051-1056, 1995
  4. Tang AM et al. Low serum vitamin B12 concentrations are associated with faster human immunodeficiency virus type 1 disease progression. Journal of Nutrition 127: 345-351, 1997
  5. Beach RS et al. Plasma vitamin B12 level as a potential cofactor in studies of human immunodeficiency virus type 1-related cognitive changes. Arch Neurol 49: 501-506, 1992
  6. Richman D et al. The toxicity of AZT in the treatment of patients with AIDS and ARC: a double blind placebo controlled trial. NEJM 317:192-197, 1987
  7. McCutchan JA et al. Cyanacobalamine (vitamin B12) supplementation does not prevent the haematologic toxicity of AZT. Fifth International Conference AIDS, Montreal, abstract MBP 325, 1989
  8. Beach R Nutritional aspects of HIV infection. PAAC Notes 11-12: 222-223, 1989

Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

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