A Tums a day could keep B12 malabsorption away, say researchers who studied the effects of metformin on vitamin B12 absorption. Metformin, sold under the brand name Glucophage, is an oral agent prescribed for type 2 diabetes.

In a study of 14 people who switched from sulfonylureas to Glucophage and a control group of seven individuals who remained on sulfonylureas, researchers found that the Glucophage group experienced reduced levels of vitamin B12.

Researchers publishing in the September 2000 issue of Diabetes Care say there is evidence that vitamin B12 is not being properly absorbed in up to 30 percent of people who take Glucophage on a continuing basis. In their study, they found that inadequate absorption from the intestinal tract is apparently caused by altered intestinal calcium metabolism.

Baseline measurements taken at the beginning of the study showed no significant difference in the total serum vitamin B12 absorption between the groups. Serum vitamin B12 is the total amount of B12 found in the bloodstream.

However, after three months of Glucophage therapy, the group showed a drop in serum vitamin B12 of more than 25 percent. At the same time, the amount of B12 that was absorbed into the body fell by about 36 percent. The good news is that daily supplements of 1.2 grams per day of calcium carbonate in the form of Tums partially reversed the drop in B12 absorbtion, by about 27 percent.

Vitamin B12 is necessary for the formation of red blood cells. B12 deficiency can lead to memory loss, fatigue and mental confusion. It can also result in peripheral nerve damage, which could be confused with nerve damage caused by diabetes.

Researchers say Glucophage may act as a calcium channel blocker. Individuals taking it may need to take supplemental calcium, particularly if they do not consume milk or other dairy products on a daily basis. Patients taking Glucophage should also be monitored for vitamin B12 deficiencies.