Metformin is primarily prescribed to help lower blood sugar levels in people with prediabetes and type 2 diabetes. It does its job so well that the American Diabetes Association (ADA) considers it a first-line diabetes drug, meaning that it is both effective and has relatively few side effects.
However, some people do experience adverse effects, or develop another medical reason to stop taking the medication. But stopping metformin on your own can have serious consequences on your health. Here's what you need to know.
How Metformin Works
Glucose, aka blood sugar, is the body's main source of energy. The body gets glucose from two places: the carbohydrates in food, and the liver. Metformin works to reduce blood glucose levels from both of these sources, as described by a study published in the November 2013 issue of Pharmacogenet Genomics.
Once the body converts the carbohydrates in food into glucose, the hormone insulin moves the glucose out of the blood and into the cells, which use it for energy. But people with prediabetes and type 2 diabetes are resistant to insulin's effects, meaning that not enough glucose gets into their cells, according to the Mayo Clinic. This causes a buildup of glucose in the bloodstream, called hyperglycemia (high blood sugar). Metformin helps correct this by improving cells' ability to use insulin.
When the body isn't getting energy from food (such as overnight, or between meals), the liver steps in and releases glucose to fuel the cells, according to the University of California, San Francisco. Metformin lowers blood sugar levels throughout the day by limiting the amount of glucose released by the liver.
Metformin doesn't cure prediabetes or type 2 diabetes, but it does help reduce the symptoms and risks of chronic high blood sugar. That's why, if you have diabetes, stopping metformin can have adverse effects on your health.
The Effects of Stopping Metformin
Elizabeth Halprin, MD, clinical director of adult diabetes at the Joslin Diabetes Center in Boston, spoke with LIVESTRONG.com about the consequences of stopping metformin. "Metformin works very well in lowering blood glucose levels," she says. "If a person stops taking metformin, their blood glucose levels will go right up."
Stopping metformin won't cause the body to go into any kind of shock or metformin withdrawal, but Dr. Halprin says it will have an adverse impact on overall health. "The short- and long-term consequences are that blood sugars will go up," she notes. "[Type 2 diabetes] will not be treated unless you substitute metformin with another medication."
- Frequent urination
- Increased thirst
- Blurred vision
Stopping metformin may also increase the risk of anxiety or depression. According to an analysis published in the February 2019 issue of Frontiers in Psychiatry, emerging research shows that metformin may help alleviate the symptoms of depression for people with type 2 diabetes.
- Cardiovascular disease
- Kidney damage or kidney failure
- Bone and joint problems
- Tooth and gum infections
- Damage to the blood vessels of the eyes, potentially causing blindness
- Nerve damage, which may lead to erectile dysfunction and can affect sexual health
- Poor blood flow in the feet, potentially causing skin infections, ulcerations and, in severe cases, amputation
Never stop taking metformin without consulting your doctor first. If you want to stop taking metformin due to adverse side effects, consider switching to an alternative form of the medication, such as metformin extended-release (also called metformin HCL). It is known to be easier on the stomach, especially if you take it with meals (which can lessen some of the side effects).
Medical Reasons for Stopping Metformin
There are a number of reasons why a doctor might stop prescribing metformin to a patient. One of these is type 2 diabetes remission, wherein the patient's overall condition has improved to the point that diabetes medication is no longer needed, according to University of Wisconsin-Madison Health.
Dr. Halprin says that people may also need to stop taking metformin if they develop acute kidney disease. But she notes that today's clinicians understand the effects of metformin and kidney disease much better than they did in the past. "We have more definitive guidelines, so a person doesn't have to stop [metformin completely]," she says. "They can [just] decrease the dose."
What to Do if You Miss a Dose
According to the Mayo Clinic, the best thing to do if you accidentally miss a dose is to simply take the metformin as soon as possible. However, if you're close to the time when you normally take your metformin, you should wait and take it at your regular time. Do not double dose.
If you're concerned about missing one or more doses of metformin, contact your doctor, who can help you get back on track.
- Mayo Clinic: "Type 2 Diabetes Overview"
- Pharmacogenet Genomics: "Metformin pathways: pharmacokinetics and pharmacodynamics"
- University of California, San Francisco: "The Liver & Blood Sugar"
- American Diabetes Association: "Hyperglycemia"
- Frontiers in Psychiatry: "Insulin Resistance as a Shared Pathogenic Mechanism Between Depression and Type 2 Diabetes"
- Mayo Clinic: "Hyperglycemia in diabetes"
- Diabetologia: "Metformin and the gastrointestinal tract"
- Mayo Clinic: "Metformin Proper Use"
- University of Wisconsin-Madison Health: "Type 2 Diabetes: Can You Cure It?"
- American Diabetes Association: "How to Use ADA’s Type 2 Diabetes Treatment Algorithm"