Metformin Side Effects

Brand Names: Glumetza, Glucophage, Glucophage XR, Riomet, Fortamet

Please note - some side effects for Metformin may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Metformin - for the Consumer

Metformin/Pioglitazone

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Metformin/Pioglitazone:

Cold-like symptoms; diarrhea; headache; indigestion; mild weight gain; nausea; stomach upset.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; bone pain; chest pain or discomfort; dark urine; difficult or painful urination; dizziness or lightheadedness; fainting; fast or difficult breathing; feeling of being unusually cold; general feeling of being unwell; muscle pain or weakness; pale stools; persistent loss of appetite; severe or persistent headache, nausea, or vomiting; shortness of breath; slow or irregular heartbeat; sudden unexplained weight gain; swelling of the hands, ankles, or feet; unusual stomach pain or discomfort; unusual drowsiness; unusual tiredness or weakness; yellowing of the eyes or skin.

Metformin

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Metformin:

Diarrhea; gas; headache; indigestion; nausea; stomach upset; temporary metallic taste; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain or discomfort; dizziness or lightheadedness; fast or difficult breathing; feeling of being unusually cold; fever, chills, or persistent sore throat; general feeling of being unwell; muscle pain or weakness; slow or irregular heartbeat; unusual drowsiness; unusual or persistent stomach pain or discomfort; unusual tiredness or weakness.

Metformin Extended-Release/Pioglitazone

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Metformin Extended-Release/Pioglitazone:

Cold-like symptoms; diarrhea; headache; indigestion; mild weight gain; nausea; stomach upset.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); blurred vision or other vision changes; bone pain; chest pain or discomfort; dark urine; difficult or painful urination; dizziness or lightheadedness; fainting; fast or difficult breathing; feeling of being unusually cold; general feeling of being unwell; muscle pain or weakness; pale stools; persistent loss of appetite; severe or persistent headache, nausea, or vomiting; shortness of breath; slow or irregular heartbeat; sudden unexplained weight gain; swelling of the hands, ankles, or feet; unusual stomach pain or discomfort; unusual drowsiness; unusual tiredness or weakness; yellowing of the eyes or skin.

Metformin Extended-Release Tablets

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Metformin Extended-Release Tablets:

Diarrhea; gas; headache; indigestion; nausea; stomach pain or upset; temporary metallic taste; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain or discomfort; dizziness or lightheadedness; fast or difficult breathing; feeling of being unusually cold; fever, chills, or persistent sore throat; general feeling of being unwell; muscle pain or weakness; slow or irregular heartbeat; unusual drowsiness; unusual or persistent stomach pain or discomfort; unusual tiredness or weakness.

Metformin Solution

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Metformin Solution:

Diarrhea; gas; headache; indigestion; nausea; stomach upset; temporary metallic taste; vomiting.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain or discomfort; dizziness or lightheadedness; fast or difficult breathing; feeling of being unusually cold; fever, chills, or persistent sore throat; general feeling of being unwell; muscle pain or weakness; slow or irregular heartbeat; unusual drowsiness; unusual or persistent stomach pain or discomfort; unusual tiredness or weakness.

Metformin Side Effects - for the Professional

Metformin

In a U.S. double-blind clinical study of Metformin hydrochloride tablets in patients with type 2 diabetes, a total of 141 patients received Metformin hydrochloride tablet therapy (up to 2550 mg per day) and 145 patients received placebo. Adverse reactions reported in greater than 5% of the Metformin hydrochloride tablet patients, and that were more common in Metformin hydrochloride tablet- than placebo-treated patients, are listed in Table 9.

Diarrhea led to discontinuation of study medication in 6% of patients treated with Metformin hydrochloride tablets. Additionally, the following adverse reactions were reported in ≥ 1.0 to ≤ 5.0% of Metformin hydrochloride tablet patients and were more commonly reported with Metformin hydrochloride tablets than placebo: abnormal stools, hypoglycemia, myalgia, lightheaded, dyspnea, nail disorder, rash, sweating increased, taste disorder, chest discomfort, chills, flu syndrome, flushing, palpitation.

Pediatric Patients

In clinical trials with Metformin hydrochloride tablets in pediatric patients with type 2 diabetes, the profile of adverse reactions was similar to that observed in adults.

Side Effects by Body System

General

Metformin has been generally well tolerated. About 20% of patients experienced mild, transient side effects sometime during therapy.

Metabolic

Lactic acidosis is a medical emergency requiring immediate evaluation and treatment. The case fatality rate may be as high as 50.3%. Patients taking metformin who present with even vague medical illnesses such as myalgia, malaise, somnolence, abdominal discomfort, and so forth, should be evaluated for a metabolic etiology like lactic acidosis.

Signs and symptoms of severe acidosis may include vomiting, abdominal pain, nausea, dyspnea, hypothermia, hypotension, and bradycardia.

Laboratory evaluation of metformin-induced lactic acidosis generally includes determination of the following: blood glucose concentration, lactic acid concentration, serum electrolytes, blood pH, metformin concentration, and exclusion of ketoacidosis.

If lactic acidosis is present, immediate institution of general supportive care is indicated. Prompt hemodialysis is also generally recommended in order to correct the acidosis and remove metformin. Hemodialysis often results in rapid improvement. Some investigators have suggested that dialysis with a bicarbonate-buffered dialysate may be particularly effective.

Metabolic side effects have included lactic acidosis, which is a potentially fatal metabolic complication. The incidence of lactic acidosis has been about 1.5 cases per 10,000 patient years. The risk of lactic acidosis has been particularly high in patients with underlying renal insufficiency. Cases of lactic acidosis occurring in patients with normal renal function have been rarely reported. Concomitant cardiovascular or liver disease, sepsis, and hypoxia have also increased the risk of lactic acidosis.

Hypoglycemia occurred uncommonly in patients receiving metformin as monotherapy. Strenuous exercise, decreased caloric intake, general debilitation, adrenal insufficiency, pituitary insufficiency, and ethanol use have increased the risk of hypoglycemia.

Gastrointestinal

Gastrointestinal effects have included nausea, anorexia, metallic taste, diarrhea, dyspepsia, flatulence, and abdominal pain. One study has reported a 20% incidence of diarrhea.

Hematologic

Hematologic side effects have included malabsorption of vitamin B12, due to intrinsic factor deficiency and possibly other mechanisms, in as many as 30% of treated patients. Megaloblastic anemia has occurred. Discontinuation of metformin or supplementation with vitamin B12 has been necessary.

Other

Other side effects include a single case of leukocytoclastic vasculitis with pneumonitis.

Hepatic

Hepatic side effects have included at least two cases of hepatitis associated with metformin use.

A 52-year-old female with a history of type II diabetes mellitus and hypertension developed lethargy, fatigue, and diarrhea after taking metformin for more than 2 weeks. After continuing metformin for a total of four weeks, her sclera became icteric and she was hospitalized. Aside from a soft systolic ejection fracture and a moderate degree of bilateral lower extremity edema, her physical examination was unremarkable. Laboratory data showed grossly elevated total bilirubin, AST, ALT, and alkaline phosphatase. Several days after her initial presentation all of her medications were discontinued. Her signs and symptoms significantly improved over the following several days, and she was discharged within two weeks of her hospitalization. The patient's presentation was considered consistent with drug-induced toxicity attributed to metformin.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date, and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This information does not endorse drugs, diagnose patients, or recommend therapy. This drug information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug of drug combination is safe, effective, or appropriate for any given patient. Drugs.com does not assume any responsibility for any aspect of healthcare administered with the aid of information provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse, or pharmacist.