Safety Information

metaformin safety

Metformin is FDA-approved to help adults with type 2 diabetes manage blood sugar levels when combined with diet and exercise. While not FDA-approved for weight loss, many leading obesity specialists and weight clinics prescribe it off-label. They believe it can aid weight loss by regulating insulin response, curbing cravings, reducing glucose production, and limiting fat storage. It works by lowering liver sugar production and enhancing muscle cell sensitivity to insulin. This dual effect improves glucose utilization and reduces insulin resistance, leading to better blood sugar control.

As with any medication, it’s important to be aware of the potential risks and benefits associated with Metformin and to use it under the guidance of a qualified healthcare provider. Regular monitoring and communication with your healthcare provider can help ensure the safe and effective use of compounded medications in your treatment regimen.

What is Metformin Used For?

Metformin is primarily used for the management of type 2 diabetes mellitus. It helps control blood sugar levels by decreasing the amount of glucose produced by the liver and enhancing insulin sensitivity in muscle cells, thereby improving the body’s response to insulin. Metformin is typically prescribed alongside dietary modifications and exercise to achieve better glycemic control in individuals with type 2 diabetes.

Warning: Risk of Lactic Acidosis

Metformin carries a warning regarding the potential risk of lactic acidosis, a rare but serious metabolic complication characterized by the buildup of lactic acid in the bloodstream. Lactic acidosis can occur due to metformin accumulation in the body, particularly in individuals with impaired kidney function or other predisposing factors such as severe infection or dehydration.

Patients should be monitored for signs and symptoms of lactic acidosis, including muscle pain or cramps, weakness, difficulty breathing, abdominal discomfort, nausea, vomiting, diarrhea, and unusual fatigue. If any of these symptoms occur, patients should seek immediate medical attention.

Who Should Not Take Metformin?

Metformin should not be taken by individuals with certain medical conditions or circumstances. Here’s a breakdown of who should not take metformin:

Individuals with severe kidney impairment:

Metformin is primarily eliminated from the body via the kidneys, so it should not be used in individuals with significantly reduced kidney function (eGFR less than 30 mL/min/1.73m²).

Those with a history of lactic acidosis:

Metformin should be avoided in individuals who have experienced lactic acidosis in the past, as it may increase the risk of recurrence.

Patients with acute or chronic metabolic acidosis:

Metformin should not be used in individuals with conditions that can lead to metabolic acidosis, as it may exacerbate this condition.

Individuals with severe liver disease:

Metformin should be used with caution or avoided in individuals with severe liver impairment, as it may exacerbate liver function abnormalities.

Pregnant or breastfeeding women:

The safety of metformin use during pregnancy and lactation is not well-established, and it should only be used if clearly needed and under the guidance of a healthcare provider.

How Should Metformin be Administered?

  • Follow the prescribed dosage instructions provided by the healthcare provider, which may vary based on individual factors such as age, medical condition, and kidney function.
  • Take metformin with meals to minimize gastrointestinal side effects. It can be taken with breakfast, lunch, and dinner or as directed by the healthcare provider.
  • Swallow tablets whole with a glass of water. Do not crush, chew, or break the tablets unless instructed otherwise by the healthcare provider.
  • If prescribed extended-release tablets, swallow them whole. Do not crush, chew, or break them, as they are designed to release the medication slowly over time.
  • Take metformin regularly and as prescribed to achieve optimal control of blood sugar levels. If you have any questions or experience adverse effects, consult your healthcare provider or pharmacist for guidance.

Foods to Avoid While Taking Metformin

While taking metformin, it’s important to be mindful of certain dietary considerations to optimize its effectiveness and minimize potential side effects. Here are some foods to avoid or limit while taking metformin:

  • Drinking alcohol excessively may increase the risk of lactic acidosis, a rare but serious complication associated with metformin use.
  • Consuming large amounts of high-carbohydrate foods may lead to spikes in blood sugar levels, which can counteract the effects of metformin.
  • High-fat meals can delay the absorption of metformin and increase the risk of gastrointestinal side effects such as nausea and diarrhea.

Common Side Effects of Metformin

  • Loose stool or diarrhea
  • Stomach cramps
  • Gas and bloating
  • And/or B12 deficiency
  • Nausea
  • Vomiting
  • Stomach pain or discomfort
  • Loss of appetite
  • Diarrhea
  • Metallic taste in the mouth

Most Serious Side Effects of Metformin

You or a caregiver must diligently monitor for these potential adverse reactions, especially when starting treatment or adjusting doses.

Lactic acidosis:
Although rare, lactic acidosis is a potentially life-threatening complication associated with metformin use. It occurs when there is an accumulation of lactic acid in the bloodstream, leading to symptoms such as muscle pain or cramps, weakness, difficulty breathing, abdominal discomfort, nausea, vomiting, and unusual fatigue. Prompt medical attention is necessary if any of these symptoms occur.

Vitamin B12 deficiency:
Long-term use of metformin may lead to decreased absorption of vitamin B12, potentially resulting in a deficiency. Symptoms of vitamin B12 deficiency include fatigue, weakness, numbness or tingling in the hands and feet, difficulty walking, and cognitive impairment.

Gastrointestinal side effects:
While common and usually mild, gastrointestinal side effects such as nausea, vomiting, diarrhea, and abdominal discomfort can occur with metformin use. These symptoms may improve over time as the body adjusts to the medication, but they can be bothersome for some individuals.

Metformin alone does not typically cause hypoglycemia (low blood sugar); however, when combined with other medications or factors that lower blood sugar, such as insulin or excessive alcohol consumption, hypoglycemia may occur. Symptoms of hypoglycemia include sweating, shakiness, dizziness, hunger, confusion, and difficulty concentrating.

Allergic reactions:
Although rare, some individuals may experience allergic reactions to metformin, characterized by symptoms such as rash, itching, swelling of the face, lips, or throat, and difficulty breathing. Seek immediate medical attention if any signs of an allergic reaction occur.


Please note that these warnings serve to highlight specific risks associated with Metformin and are not comprehensive. Healthcare providers should review the full prescribing information for Metformin and consider individual patient factors before prescribing this medication. Patients should consult their healthcare provider for personalized guidance and recommendations regarding the use of Metformin and the management of any potential risks.