Metformin is an oral drug that decreases insulin resistance and lowers blood glucose levels in type 2 diabetics; the drug is also used for treatment of polycystic ovary disease. Like any drug, metformin can cause side effects ranging from mild to severe. Metformin doses often start low and are adjusted upward; side effects can occur at any dose.
Common Mild Side effects
The most common side effects of metformin in double blind placebo studies are diarrhea with an incidence of 53 percent and nausea and vomiting reported in 25 of trial participants. Headache, flatulence and a metallic taste in the mouth were reported in fewer than 10 percent of patients. Long-acting metformin reports fewer side effects than the shorter-acting form.
Lactic Acidosis
Metformin has a very small risk of causing lactic acidosis, a very serious complication that has an occurrence frequency of 0.06 per 1,000 patient years. Certain medical complications may increase the risk of lactic acidosis. People with kidney (renal) or liver disease should not take metformin, because both increase the risk of lactic acidosis, as do low oxygen levels (hypoxia) and alcoholism, which often causes both liver and kidney damage.
Patients undergoing surgery should discontinue metformin 48 hours or more before surgery that requires fasting because dehydration is an increased risk factor for lactic acidosis. Patients should not restart the drug until they've rehydrated after surgery.
Symptoms of metformin-induced lactic acidosis are confusion, loss of appetite, thirst, nausea, vomiting and abdominal pain. As many as 50 percent of all cases of lactic acidosis are fatal, so prompt medical treatment is essential.
Blood Sugar Fluctuations
Metformin is taken to decrease hyperglycemia (high blood sugar). While not a side effect of the medication, too low of a dose may result in hyperglycemia. Symptoms of hyperglycemia include thirst, frequent urination, a fruity smell on the breath, flushing confusion and rapid breathing.
Eating too few calories while taking metformin can result in hypoglycemia (low blood sugar). Symptoms of low blood sugar are sweatiness, lightheadedness, weakness, headache, fainting, shaking, drowsiness or confusion. Carrying hard candies or glucose tablets to treat hypoglycemia by raising blood sugar rapidly is helpful.
Allergic Reactions and Drug Interactions
Any drug can cause an allergic reaction. Signs of allergic reaction to metformin include rash, shortness of breath, itching, hives or swelling. Many other drugs interact with metformin; be sure to inform your doctor of all medications taken before starting metformin.
Member Comments