Metformin

Type 2 Diabetes Management

Metformin is primarily used to improve glycemic control in people with type 2 diabetes mellitus. It works by helping the body respond better to the insulin it produces and by reducing the amount of sugar the liver releases into the bloodstream.

How It Is Prescribed

This medication is often the first treatment recommended for type 2 diabetes. It may be used in several ways:

• As a standalone treatment: Metformin can be used alone when diet and exercise are not enough to control blood sugar levels.
• In combination: It is frequently used with other diabetes medications, such as insulin or other oral drugs, to achieve better blood sugar targets.
• For different age groups: Certain forms of metformin are approved for use in adults and children 10 years of age and older.

Limitations of Use

Metformin is specifically for type 2 diabetes. It is not used to treat type 1 diabetes, a condition where the body does not produce insulin at all. It is also not used for treating diabetic ketoacidosis.

How Metformin Works

Metformin belongs to a class of drugs called biguanides. It helps manage blood glucose (sugar) levels through three primary mechanisms:

• Reducing sugar production: It decreases the amount of glucose that the liver produces and releases into the bloodstream.
• Improving insulin sensitivity: It makes the body's tissues, such as muscle, more sensitive to insulin. This helps the body use its own insulin more effectively to move sugar out of the blood and into the cells.
• Decreasing sugar absorption: It reduces the amount of glucose absorbed from the intestines after eating.

Unlike some other diabetes medications, metformin does not cause the pancreas to produce more insulin. Because it does not increase insulin levels, it is less likely to cause dangerously low blood sugar (hypoglycemia) when used as a standalone treatment. It is typically used in combination with diet and exercise to improve glycemic control in adults and children with type 2 diabetes.

Common Side Effects

Many people experience digestive symptoms when they first start taking metformin. These effects often go away after a few weeks. Common side effects include:

• Diarrhea
• Nausea or vomiting
• Stomach pain or gas
• Bloating or indigestion
• Heartburn
• Metallic taste in the mouth
• Headache
• Flushing of the skin
• Muscle pain

Serious Side Effects

Contact your doctor immediately or seek emergency care if you experience any of the following serious symptoms:

• Extreme tiredness, weakness, or discomfort
• Slow or irregular heartbeat
• Shortness of breath or difficulty breathing
• Severe stomach pain with nausea and vomiting
• Unusual muscle pain
• Feeling cold, especially in the arms and legs
• Dizziness or lightheadedness
• Rash or skin reactions
• Chest pain

Long-term use of metformin may also lead to low levels of vitamin B12 in the blood. Your healthcare provider may monitor your B12 levels periodically through blood tests.

Lactic Acidosis

Metformin has a boxed warning regarding the risk of lactic acidosis. This is a rare but life-threatening buildup of lactic acid in the blood. It can occur if the medication accumulates, often due to decreased kidney function.

Risk factors for lactic acidosis include:

• Severe kidney impairment.
• Being 65 years of age or older.
• Having a radiological study that uses contrast dye.
• Surgery or other procedures.
• Conditions that cause low oxygen levels (hypoxia), such as heart failure.
• Excessive alcohol intake.
• Liver impairment.

Contraindications

Metformin is contraindicated in patients with severe renal impairment (an eGFR below 30 mL/min/1.73 m²). It should also not be used by individuals with acute or chronic metabolic acidosis, including diabetic ketoacidosis.

Vitamin B12 Levels

Long-term use of metformin has been associated with a decrease in vitamin B12 levels. Periodic monitoring of B12 levels is often recommended, especially for those at risk of deficiency or anemia.

Blood Sugar Levels

While metformin alone typically does not cause low blood sugar (hypoglycemia), the risk increases when it is taken with other diabetes medications like insulin or sulfonylureas. Monitoring blood glucose levels is a standard part of management.

Pregnancy

Maintaining stable blood sugar levels is important during pregnancy to reduce the risk of complications for both the parent and the developing baby. Metformin is sometimes used to treat gestational diabetes or type 2 diabetes during pregnancy, although insulin is often the preferred treatment for managing blood sugar in these cases. Metformin is known to cross the placenta and reach the fetus. While current evidence does not show a clear link between metformin and an increased risk of major birth defects, the long-term impact on the child's health is still being studied.

Metformin may also trigger ovulation in some premenopausal women who do not ovulate regularly, which can increase the risk of unintended pregnancy. Individuals should consult with a healthcare professional about effective contraception if they do not wish to become pregnant while taking this medication.

Breastfeeding

Metformin is excreted into breast milk in small amounts. Most research suggests that the levels reaching the infant are low and unlikely to cause significant harm. However, because every situation is different, breastfeeding individuals should talk to their doctor to weigh the benefits of breastfeeding against any potential risks to the infant. Monitoring the infant for proper growth and development is typically recommended.

Oral Tablet Forms

Metformin is most commonly prescribed as a tablet. There are two main types of tablets available:

• Immediate-release tablets: These tablets release the medication into the body shortly after they are swallowed.
• Extended-release tablets: These are designed to release the medication slowly over a longer period. These versions are often labeled with suffixes such as ER, XR, or XL.

Liquid Forms

For patients who have difficulty swallowing pills, metformin is available in liquid formats:

• Oral solution: A clear liquid form of the medication.
• Oral suspension: A liquid form that contains particles of the medication and typically requires shaking before each dose.

FDA Approval and Indications

Metformin was approved by the FDA in 1994 for the treatment of type 2 diabetes mellitus. It is intended for use alongside diet and exercise to improve blood glucose control in adults and children aged 10 and older.

Boxed Warning

Metformin carries a boxed warning regarding lactic acidosis, a rare but serious metabolic complication. This condition can occur if metformin builds up in the blood. Risk factors include:

• Severe kidney impairment
• Age 65 or older
• Radiological studies using iodine contrast
• Surgery or other procedures
• Conditions that cause low blood oxygen, such as heart failure
• Excessive alcohol intake
• Liver impairment

Kidney Function Guidelines

In 2016, the FDA updated metformin labeling to allow its use in patients with mild to moderate kidney impairment. The agency transitioned from using blood creatinine levels to the estimated glomerular filtration rate (eGFR) to measure kidney function. Metformin is contraindicated in patients with an eGFR below 30 mL/min/1.73 m2, and initiation is not recommended for those with an eGFR between 30 and 45 mL/min/1.73 m2.

Safety Recalls

The FDA has monitored and issued communications regarding N-Nitrosodimethylamine (NDMA) impurities in certain extended-release metformin products. This led to voluntary recalls by several manufacturers after testing showed NDMA levels above the acceptable intake limit.

Metformin and Weight

Metformin is primarily used to manage blood sugar levels in people with type 2 diabetes. Although it is not approved by the FDA as a weight-loss drug, some people may lose a modest amount of weight while taking it. This weight loss usually occurs slowly over several months and is not guaranteed for everyone.

The reasons for weight loss while taking metformin are not entirely clear, but several factors may contribute:

• Changes in appetite: Some users report feeling less hungry or feeling full more quickly after eating.
• Digestive side effects: Common side effects such as nausea, diarrhea, or stomach discomfort may lead to a temporary decrease in food intake.
• Metabolic effects: Metformin improves how the body responds to insulin, which may influence how the body stores and uses energy.

Weight loss is most effective when the medication is used alongside a healthy diet and regular exercise. Unlike some other diabetes medications, such as insulin or sulfonylureas, which are often associated with weight gain, metformin is generally considered weight-neutral or associated with slight weight reduction. If the medication is stopped, any weight lost during treatment may be regained.