Metformin is a common prescription drug used to treat type 2 diabetes. It works by reducing glucose production in the liver, decreasing absorption of glucose in the intestines, and improving insulin sensitivity so the body uses insulin more efficiently.
While metformin is generally well-tolerated, it can cause some side effects. Being aware of the potential side effects can help you recognize and address problems early on.
Gastrointestinal Side Effects
The most common side effects of metformin involve the digestive system. About 30% of people taking metformin experience nausea, diarrhea, vomiting, gas, or abdominal pain and discomfort.
These symptoms often go away on their own within 2 to 3 weeks as your body adjusts to the medication. Taking your metformin dose during or immediately after meals may also help reduce stomach issues.
In some cases, gastrointestinal side effects persist. Talk to your doctor if you still have diarrhea or abdominal discomfort after 3 or 4 weeks on the medication, as they may need to adjust your dosage.
Risk of B12 Deficiency
Long-term use of metformin may interfere with your body’s ability to absorb vitamin B12 from food, leading to B12 deficiency. Symptoms of B12 deficiency include fatigue, muscle weakness, and tingling or numbness in the extremities.
To reduce this risk, your doctor may recommend taking a vitamin B12 supplement while on metformin or checking your B12 levels periodically. Addressing a B12 deficiency early on can prevent long-term complications.
Other Possible Side Effects
A few people may experience headaches, body aches, or muscle pain while on metformin. Metformin and hair loss, though rare, have been reported as potential side effects of the medication by a small number of users.
In most cases, these minor side effects go away in 1 to 2 weeks without treatment. But if they persist for more than two weeks, speak with your doctor about adjusting your dosage or switching medications. They may be signs that your body isn’t tolerating metformin well.
Decreased absorption of thyroid medications and changes in their effectiveness have also been reported with long-term metformin use in some cases.
When to See Your Doctor
In most cases, the symptoms you experience when starting metformin should go away within 2 to 3 weeks as your body adjusts.
But speak to your doctor right away if you have:
- Persistent vomiting, nausea, or diarrhea
- Persistent or worsening abdominal discomfort
- Muscle pain, weakness, or fatigue that persists
- Signs of a B12 deficiency, like tingling in the hands and feet
- Dark urine or yellow skin and eyes, which may indicate liver problems
Alert your doctor to any persistent or troublesome side effects when taking metformin so they can determine if adjustments to your dosage or medication regimen may be needed.
Benefits Still Likely Outweigh Risks
While metformin can cause some unpleasant side effects for most people, the benefits of tighter blood sugar control and reduced risk of diabetes complications still far outweigh these risks.
Work closely with your healthcare provider to address any persistent side effects and determine if any dosage adjustments may help.
In most cases, taking some practical steps like taking metformin with food or starting at a lower initial dose provides relief from side effects without compromising effectiveness. Don’t stop taking metformin without consulting your doctor first.
