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Metformin Side Effects

In Summary

Commonly reported side effects of metformin include: lactic acidosis, diarrhea, nausea, nausea and vomiting, vomiting, and flatulence. Other side effects include: asthenia, and decreased vitamin b12 serum concentrate. See below for a comprehensive list of adverse effects.

For the Consumer

Applies to metformin: oral solution, oral tablet, oral tablet extended release

Along with its needed effects, metformin may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking metformin:

More common
  • Abdominal or stomach discomfort
  • cough or hoarseness
  • decreased appetite
  • diarrhea
  • fast or shallow breathing
  • fever or chills
  • general feeling of discomfort
  • lower back or side pain
  • muscle pain or cramping
  • painful or difficult urination
  • sleepiness
Less common
  • Anxiety
  • blurred vision
  • chest discomfort
  • cold sweats
  • coma
  • confusion
  • cool, pale skin
  • depression
  • difficult or labored breathing
  • dizziness
  • fast, irregular, pounding, or racing heartbeat or pulse
  • feeling of warmth
  • headache
  • increased hunger
  • increased sweating
  • nausea
  • nervousness
  • nightmares
  • redness of the face, neck, arms, and occasionally, upper chest
  • seizures
  • shakiness
  • shortness of breath
  • slurred speech
  • tightness in the chest
  • unusual tiredness or weakness
Rare
  • Behavior change similar to being drunk
  • difficulty with concentrating
  • drowsiness
  • lack or loss of strength
  • restless sleep
  • unusual sleepiness

Some side effects of metformin may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common Less common
  • Abnormal stools
  • bad, unusual, or unpleasant (after) taste
  • change in taste
  • difficulty with moving
  • discoloration of the fingernails or toenails
  • flu-like symptoms
  • joint pain
  • metallic taste in mouth
  • rash
  • runny nose
  • sneezing
  • stuffy nose
  • swollen joints

For Healthcare Professionals

Applies to metformin: compounding powder, oral solution, oral tablet, oral tablet extended release

General

Gastrointestinal events such as nausea, vomiting, diarrhea, abdominal pain, and loss of appetite have been frequently reported during therapy initiation and resolve spontaneously in most cases.

Adverse events in the pediatric population appear to be similar in nature and severity to that published in adults.[Ref]

Metabolic

Common (1% to 10%): Hypoglycemia
Very rare (less than 0.01%): Lactic acidosis[Ref]

Gastrointestinal

Very common (10% or more): Diarrhea (53.2%), nausea/vomiting (25.5%), flatulence (12.1%)
Common (1% to 10%): Indigestion, abdominal discomfort, abnormal stools, dyspepsia, loss of appetite[Ref]

Hematologic

Very rare (less than 0.01%): Subnormal vitamin B12 levels[Ref]

Other

Common (1% to 10%): Asthenia, chills, flu syndrome, accidental injury[Ref]

Hepatic

Very rare (less than 0.01%): Liver function test abnormalities, hepatitis[Ref]

Cardiovascular

Common (1% to 10%): Chest discomfort, flushing, palpitation[Ref]

Dermatologic

Common (1% to 10%): Rash, nail disorder, increased sweating
Very rare (less than 0.01%): Erythema, pruritus, urticaria[Ref]

Endocrine

Frequency not reported: Reduction in thyrotropin (TSH) levels[Ref]

Immunologic

Very common (10% or more): Infection (20.5%)[Ref]

Musculoskeletal

Common (1% to 10%): Myalgia[Ref]

Nervous system

Common (1% to 10%): Lightheadedness, taste disturbances[Ref]

Psychiatric

Common (1% to 10%): Headache[Ref]

Respiratory

Common (1% to 10%): Rhinitis[Ref]

References

1. "Product Information. Fortamet (metFORMIN)." Physicians Total Care, Tulsa, OK.

2. "Product Information. Glucophage (metformin)." Bristol-Myers Squibb, Princeton, NJ.

3. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

4. Cerner Multum, Inc. "Australian Product Information." O 0

5. "Product Information. Glumetza (metFORMIN)." Biovail Pharmaceuticals Canada, Mississauga, IA.

6. "Product Information. Riomet (metFORMIN)." Ranbaxy Pharmaceuticals, Jacksonville, FL.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Some side effects may not be reported. You may report them to the FDA.

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