Metformin and Grapefruit

by on May 14, 2012

Metformin (Glucophage, Glumetza), used to treat people with type 2 diabetes, is an oral medication used to lower blood glucose levels. Like many medications, Metformin is known to have some food and drug interactions that can have a negative effect on the body, but grapefruit is not one of them.

Grapefruit and grapefruit juice, in general, are known to have an interaction with many different drugs, but there is no direct evidence of a negative interaction between this substance and Metformin.

Chemicals found in grapefruit can affect the absorption and therefore effectiveness of certain medications. In some cases, grapefruit can decrease the levels of drug in the bloodstream making it ineffective; in rare instances, however, it can actually have the opposite effect, increasing the levels of drug in the system andputting patients at risk of having too much of their medication in their bloodstream. The general consensus at this point is that grapefruit juice, however, does not interact with Metformin.


Though most studies have found no interaction between Metformin and grapefruit, a study in 2009 produced an unfavourable result when studying a rat population. Dr. Owira, a pharmacologist from the South African University, noted that the combination raised lactic acid in the rat population, which in turn caused low Ph levels in the body, negatively affecting the metabolism. As this result has not been reproduced, Dr. Owira has not recommended people cut grapefruit consumption completely and has instead suggested additional research to see if the phenomenon also applied to humans.

Current Status

The current status of Metformin with grapefruit consumption is that pharmacists and doctors do not acknowledge an association. The FDA does not give any warnings regarding possible negative interactions with this combination, and until further testing indicates problems, it is considered safe. As there is some research suggesting that grapefruit and grapefruit juice can help stabilize blood sugar levels, and Metformin is used to treat those with blood sugar issues, discussing the use of these two substances in combination with your doctor is advisable.

If there is any concern of effectiveness of the drug, a fear of interaction, or if you feel you consume large amounts of grapefruits or any other substance known to have an impact on medication, you may wish to discuss these issues with your doctor. As it stands, however, this interaction is not currently prohibited with the treatment.