Metformin is a medication primarily prescribed to treat type 2 diabetes mellitus, a chronic condition characterized by high levels of sugar (glucose) in the blood. It belongs to a class of drugs known as biguanides.

How Does Metformin Work?

Metformin works by decreasing the amount of glucose produced by the liver and improving the body’s response to insulin, a hormone that helps regulate blood sugar levels. Additionally, it increases the uptake of glucose by muscle cells, thereby lowering blood sugar levels.

Precautions and Warnings with Metformin

Metformin is a prescription medication and can only be prescribed by a licensed physician. It would be best to discuss your medical history and current lifestyle truthfully with your prescriber.


  • Metformin should not be used in individuals with severe kidney impairment or kidney failure, as it can increase the risk of lactic acidosis, a rare but serious condition.
  • Patients with certain medical conditions such as liver disease, heart failure, or severe respiratory disease should use Metformin cautiously and under close medical supervision.

Warnings Regarding Specific Populations

  • Pregnant women should only use Metformin under the guidance of a healthcare professional, as its safety during pregnancy is not well-established.
  • Metformin may pass into breast milk, so breastfeeding mothers should consult their healthcare provider before using this medication.
  • Elderly patients may be more susceptible to the side effects of Metformin and may require dosage adjustments.

 Metformin Side Effects

Metformin may interact with other medications, supplements, or substances, potentially affecting its effectiveness or increasing the risk of adverse effects. Some notable drug interactions with Metformin include:

Common Side Effects

  • Stomach problems:
    • Diarrhea
    • Nausea
    • Stomach pain
    • Heartburn
    • Gas

Serious Side Effects

  • Lactic acidosis. Symptoms can include:
    • Tiredness
    • Weakness
    • Unusual muscle pain
    • Trouble breathing
    • Unusual sleepiness
    • Stomach pains, nausea, or vomiting
    • Dizziness or lightheadedness
    • Slow or irregular heart rate
  • Hypoglycemia (low blood sugar). Symptoms can include:
    • Headache
    • Weakness
    • Confusion
    • Shaking or feeling jittery
    • Drowsiness
    • Dizziness
    • Irritability
    • Sweating
    • Hunger
    • Fast heart rate
  • Low vitamin B12 levels. Symptoms can include:
    • Low energy
    • Muscle weakness
    • Loss of appetite
    • Tingling or numbness in the hands or feet

Drug Interactions With Metformin

Metformin may interact with other medications, supplements, or substances, potentially affecting its effectiveness or increasing the risk of adverse effects. Some notable drug interactions with Metformin include:

  • other diabetes medications that lower your blood sugar level, such as insulin
  • the cholesterol supplement nicotinic acid
  • certain seizure drugs, including topiramate or phenytoin (Dilantin)
  • the heartburn drug cimetidine
  • certain antipsychotic drugs, such as chlorpromazine
  • some hormone medications, including birth control pills
  • certain blood pressure medications, such as hydrochlorothiazide
  • steroid medications, such as prednisone
  • thyroid medications, including levothyroxine (Synthroid)
  • the tuberculosis medication isoniazid
  • the HIV medication dolutegravir (Tivicay)

Strengths and Dosages of Metformin

Available Strengths

Metformin is available in various strengths, including 500 mg, 850 mg, and 1000 mg tablets. Extended-release formulations are also available for some strengths, such as 500 mg and 750 mg.

Recommended Dosages

For most adults with type 2 diabetes, the initial dose is typically 500 mg to 1000 mg taken orally once or twice daily with meals. Dosage adjustments may be necessary based on blood sugar levels and kidney function.

Metformin Alternatives

While Metformin is a commonly prescribed medication for the management of type 2 diabetes mellitus, there are several alternative medications available that healthcare providers may consider based on individual patient factors and treatment goals:

  • Sulfonylureas: These medications, such as glyburide and glipizide, work by stimulating insulin secretion from the pancreas. They can be used as monotherapy or in combination with other antidiabetic agents.
  • DPP-4 inhibitors (Dipeptidyl peptidase-4 inhibitors): Drugs like sitagliptin and saxagliptin enhance insulin secretion and reduce glucagon production, leading to improved glycemic control. They are often prescribed as adjunctive therapy to Metformin or other antidiabetic medications.
  • GLP-1 receptor agonists (Glucagon-like peptide-1 receptor agonists): Medications such as exenatide and liraglutide mimic the action of GLP-1 (such as Victoza and Saxenda), a hormone that stimulates insulin secretion and inhibits glucagon release. GLP-1 receptor agonists are administered via injection and are typically used in patients who have not achieved glycemic control with other therapies.
  • SGLT2 inhibitors (Sodium-glucose cotransporter-2 inhibitors): Drugs like canagliflozin (Invokana) and dapagliflozin reduce renal glucose reabsorption, leading to increased urinary glucose excretion and lower blood glucose levels. They are often prescribed as adjunctive therapy to Metformin or as monotherapy in patients unable to tolerate Metformin.

Questions and Answers of Metformin

What is Metformin used for?

Metformin is primarily used for the management of type 2 diabetes mellitus, a condition characterized by high blood sugar levels resulting from insulin resistance or insufficient insulin production. It helps control blood glucose levels by decreasing the amount of glucose produced by the liver and improving insulin sensitivity in peripheral tissues.

How does Metformin work?

Metformin works through multiple mechanisms to lower blood glucose levels. It inhibits gluconeogenesis, the process by which the liver produces glucose, and enhances insulin sensitivity in muscle cells, allowing them to take up glucose more effectively. Additionally, Metformin may also reduce intestinal glucose absorption and improve lipid metabolism.

What are the dangers of taking Metformin?

While Metformin is generally considered safe and well-tolerated, there are some potential risks associated with its use. Rare but serious side effects include lactic acidosis, a potentially life-threatening condition characterized by the accumulation of lactic acid in the bloodstream. Other adverse effects may include gastrointestinal disturbances such as diarrhea, nausea, and abdominal discomfort.

When to take Metformin?

Metformin is usually taken orally with meals to reduce gastrointestinal side effects. It is important to take Metformin consistently at the same time each day to maintain steady blood levels of the medication.

How long does Metformin take to work?

Metformin begins to exert its therapeutic effects shortly after administration, with improvements in blood glucose levels typically observed within one to two weeks of starting treatment. However, it may take several weeks or months to achieve optimal glycemic control, and dosage adjustments may be needed over time.

How does Metformin help you lose weight?

Metformin may help reduce appetite, promote satiety, and improve insulin sensitivity, leading to decreased food intake and enhanced fat utilization by the body. Weight loss with Metformin is often modest but can be beneficial for overall health and glycemic control.

When is the best time to take Metformin?

The timing of Metformin administration may vary depending on individual preferences and lifestyle factors. Some people prefer to take it with breakfast, lunch, and dinner, while others may find it more convenient to take it at specific times of the day, such as morning and evening.

What does Metformin do for PCOS?

Metformin is commonly used off-label in the treatment of polycystic ovary syndrome (PCOS), a hormonal disorder characterized by irregular menstrual periods, ovarian cysts, and hyperandrogenism. It helps improve insulin sensitivity, regulate menstrual cycles, and reduce androgen levels, which can alleviate symptoms of PCOS and improve fertility outcomes.

How long does Metformin stay in your system?

Metformin has a half-life of approximately 6.2 hours, meaning it takes about this amount of time for half of the medication to be eliminated from the body. However, it may take several days for Metformin to be completely cleared from the system after discontinuation.

What foods should I avoid when taking Metformin for PCOS?

While there are no specific dietary restrictions associated with Metformin use for PCOS, some individuals may experience gastrointestinal side effects when consuming certain foods high in carbohydrates or sugars. It is advisable to follow a balanced diet that includes a variety of nutrient-rich foods and to avoid excessive intake of processed sugars and high-fat foods.

Can I stop taking Metformin when my sugar goes back to normal?

Even if your blood sugar levels have normalized, stopping Metformin abruptly can lead to rebound hyperglycemia and may increase the risk of diabetes-related complications. Your healthcare provider will determine the most appropriate course of action based on your individual health status and treatment goals.

What is the benefit of taking Metformin at night?

By taking Metformin before bedtime, it may help mitigate the dawn phenomenon, a natural rise in blood sugar levels that occurs in the early morning hours. However, individual responses to nighttime dosing may vary.

IMPORTANT NOTE: The information provided here is for educational purposes only and is not intended to serve as medical advice, diagnosis, or treatment recommendations. It should not be taken as an endorsement of any specific medication or treatment. Individual health conditions and responses to treatment can vary greatly; therefore, this information should not be seen as a guarantee of safety, suitability, or effectiveness for any particular individual. Always consult with a healthcare professional for personalized medical advice and before making any decisions regarding your health or treatment plans.

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