How Much B-12 Should I Take With Metformin?

The recommended daily dose of vitamin B-12 for children and adolescents ages 4 to 13 is between 1.2 mcg and 1.8 mcg, the Office of Dietary Supplements notes. People aged 14 and up need about 2.4 mcg of vitamin B-12 daily. Pregnant women require 2.6 mcg/day, while lactating women need 2.8 mcg/day. These intake levels do not apply to people who suffer from vitamin B-12 deficiency. They usually require higher doses of vitamin B-12 to treat their condition. Consult your doctor before taking vitamin B-12 supplements to determine a dose appropriate for your needs.

How much metformin you take and the duration you take it affect your risk of developing vitamin B-12 deficiency, according to a study published in a 2006 issue of the journal "Archives of Internal Medicine." The study had 155 participants who suffered from vitamin B-12 deficiency resulting from metformin use. The results of the study indicated that each 1 g daily of metformin caused a ratio of 2.88 increase in the risk of developing vitamin B-12 deficiency. Patients using metformin for three or more years had a lower ratio of 2.39. This suggests that it is possible to use metformin, by dosage and duration of treatment, as a basis for devising a method of preventing vitamin B-12 deficiency. The results also help determine how much supplementation is needed to maintain healthy levels of the vitamin B-12.

Treating metformin-induced vitamin B-12 deficiency requires vitamin B-12 injections of 1 mg a year, according to an article published in a 2010 issue of the "Journal of Young Pharmacists." The article examined previous studies involving vitamin B-12 deficiency and long-term metformin use. One of the difficulties of treating metformin-induced vitamin B-12 deficiency is finding a dose of the vitamin that is cost-effective but also helpful in preventing potential complications brought on by deficiency, such as neuropathy. The study determined that annual 1 mg doses of vitamin B-12 helped replenish depleted vitamin B-12 stores but also remained cost-effective and lasted about a year.

Treating vitamin B-12 deficiency generally involves the use of either oral or intramuscular vitamin B-12 supplements, according to the American Family Physician website. The initial deficiency treatment dose for oral vitamin B-12 supplements is between 1,000 mcg daily and 2,000 mcg daily for one to two weeks. The maintenance dose drops to 1,000 mcg daily for life after the initial dosing period. The initial dose for intramuscular vitamin B-12 is between 100 mcg and 1,000 mcg every day or every other day for about one to two weeks. After the initial period of intramuscular treatment, the frequency decreases to every one or three months.