Metformin Side Effects on the Heart

Metformin, sold under the brand name Glucophage, is an anti-hyperglycemic medication used alone or in combination with other medication, such as insulin, to control blood glucose levels in those with Type 2 diabetes 1. It belongs in the biguanide class of medication. According to, metformin works by decreasing the amount of glucose obtained from food and glucose produced by the liver, lowering blood glucose levels 12.

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If you are experiencing serious medical symptoms, seek emergency treatment immediately.

Lactic Acidosis

According to, the chemical structure of metformin resembles that of the French lilac plant, which was used long ago to lower blood sugar but found to be too toxic 12. Metformin is shorter-acting than French lilac and can in rare cases produce the same toxic reaction, called lactic acidosis 1. Lactic acidosis--which can be fatal--is a condition in which there is too much lactate in the blood, which lowers the pH. It can occur when metformin levels build up and cannot be cleared from the body 1. Symptoms of lactic acidosis include slow heartbeat, or bradycardia, and low blood pressure, or hypoptension. Other symptoms include shallow breathing, diarrhea and extreme weakness and fatigue. Alcohol consumption and a reaction with the medication Tagamet can increase the chances for lactic acidosis to develop. Metformin should not be taken by those with congestive heart failure or heart disease 1.

Chest Pain

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Chest pain is a rare but serious side effect of taking metformin, according to PubMed Health 13. Notify your physician immediately if you experience any chest pain while taking metformin 1. Metformin has been well studied in many clinical trials and found to be safe in most instances 1. The side effects reported by those taking metformin are compared against any side effects experienced by those taking a placebo 13. It has been determined that taking the longer-acting formula for metformin produces less chance of side effects 13. Metformin should be stored in a tightly sealed container, at room temperature and away from excess moisture and light, as found in the bathroom 1.

Heart Palpitations

According to eMedTV, it's possible for metformin to cause heart palpitations, a feeling as if the heart is racing or beating too hard 13. This is not a common side effect but must be reported to your physician immediately if it occurs. It's also possible to have an allergic reaction to metformin 1. Symptoms of a severe allergic reaction include an itchy skin rash with hives, shortness of breath and difficulty breathing, along with swelling of the face, tongue and throat. This is an emergency situation that requires immediate medical intervention.