Metformin is a first-line medication for managing high blood sugar, particularly in type 2 diabetes. It lowers glucose levels in the bloodstream without causing hypoglycemia, or dangerously low blood sugar. This medication is considered an insulin sensitizer, meaning it helps the body use its own insulin more effectively.
The Mechanism of Action
Metformin’s primary function is to reduce the amount of glucose produced by the liver, a process known as gluconeogenesis. In individuals with insulin resistance, the liver may release too much glucose. Metformin intervenes by inhibiting certain enzymes within liver cells, which curtails the liver’s excessive glucose output and helps lower overall blood sugar levels.
The medication also enhances insulin sensitivity in tissues like muscle cells. Insulin is a hormone that acts like a key, unlocking cells to allow glucose to enter for energy. Metformin makes the body’s cells more responsive to insulin, allowing them to absorb more glucose from the bloodstream and further lower blood sugar.
A third action of metformin takes place in the gastrointestinal tract. It slightly decreases the amount of glucose that is absorbed from food during digestion. Metformin also promotes an increase in glucagon-like peptide-1 (GLP-1) in the gut, a hormone that helps regulate appetite and insulin secretion.
Expected Impact on Blood Sugar Levels
While metformin begins working soon after it is taken, its full effects on blood sugar control are not immediate. Some individuals notice improvements in their daily blood glucose readings within the first week, reflecting the drug’s initial impact on glucose production and absorption.
The effectiveness of metformin is measured by the change in hemoglobin A1c (HbA1c) levels. The HbA1c test provides a long-term average of blood sugar control over two to three months. It takes this amount of time for the full benefits of metformin to be reflected in HbA1c results. On average, metformin monotherapy is expected to lower HbA1c levels by approximately 1% to 1.5%.
Additional Health Effects
Beyond its impact on glucose, metformin has other health benefits, most notably its effect on body weight. Unlike some diabetes medications that can cause weight gain, metformin is associated with modest weight loss or weight neutrality. This makes it a suitable option for many individuals with type 2 diabetes, as weight management is often a parallel health goal.
This weight effect is partly attributed to how metformin influences appetite and calorie intake. The medication can increase the secretion of a hormone known as GDF15, which acts on the brain to reduce appetite. Its impact on glucose metabolism also helps mitigate conditions that lead to weight gain.
Metformin may also have positive effects on cardiovascular health. Its ability to improve insulin sensitivity, assist with weight management, and potentially lower lipid levels contributes to a better cardiovascular risk profile.
Common Side Effects
The most frequently reported side effects of metformin are gastrointestinal. Users may experience diarrhea, nausea, abdominal discomfort, and gas, particularly when first starting the medication. These effects are often temporary and decrease as the body adjusts to the drug over several weeks.
To minimize these digestive issues, doctors recommend taking metformin with a meal. Starting with a lower dose and gradually increasing it can help the body adapt. For individuals who continue to struggle with side effects, an extended-release (ER) formulation is available, which is often better tolerated as the medication is released more slowly.
A rare but serious side effect associated with metformin is lactic acidosis, a condition where lactate builds up in the bloodstream. The risk of this complication is very low but increases significantly in individuals with severe kidney problems, as the kidneys are responsible for clearing metformin from the body. Other risk factors include severe liver disease, excessive alcohol consumption, and conditions that can lead to a lack of oxygen in the blood.