How Long Does Metformin Take to Work? 4 Signs to Look For

Key Takeaways

• Metformin is a first-line treatment for type 2 diabetes. It lowers blood glucose levels by reducing liver production and improving insulin sensitivity.
• While metformin can start lowering blood sugar within 48 hours, its full impact may take several months.
• Signs that metformin is working include lower blood sugar levels, modest weight loss, improved cholesterol levels, and better menstrual regulation for individuals with PCOS.
• If symptoms persist or you experience unmanageable side effects like stomach upset or nausea, talk to your doctor for medical advice. They may adjust your dosage, explore other treatments, or suggest lifestyle changes to help improve results.

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Metformin is a widely prescribed diabetes medication used to manage blood sugar levels. It is also known by the brand names Glucophage, Glumetza, or Fortamet. Metformin reduces the amount of sugar the body produces and absorbs while improving its utilization of insulin. 

Beyond diabetes, metformin is also used for other health conditions, such as prediabetes, insulin resistance, and polycystic ovary syndrome (PCOS). Metformin is the only medication recommended by the American Diabetes Association (ADA) for prediabetes. In some cases, it’s even prescribed to support weight management (although the FDA has not approved metformin specifically for weight loss alone).¹ 

Known for its safety and effectiveness, metformin is in a class of drugs called biguanides and is the first-choice treatment for type 2 diabetes (it’s not used to treat type 1 diabetes).¹ This article will guide you through how long metformin takes to work and how you can recognize if it’s delivering the results you need.¹

How Long Does It Take for Metformin to Work?

Metformin reduces the amount of sugar your body absorbs and produces. It can take effect within 48 hours of the first dose but may need at least 61 weeks to reach full efficacy.²

Metformin helps the liver reduce the amount of glucose it produces while increasing the body’s sensitivity to insulin. These effects take time, especially for those with more significant blood sugar dysregulation.

When is Metformin Best Taken?

Metformin is best taken consistently at the same time each day with food to help reduce the risk of stomach upset. The immediate-release form is typically taken twice daily, while the extended-release version is designed for once-daily use and is usually taken with dinner.¹

4 Signs Metformin Is Working

Metformin works gradually to improve how your body processes sugar, and there are several signs to watch for as your treatment progresses. Here are some signs that metformin may be working effectively:

• Lower Blood Sugar: If you check your blood sugar levels at home, you should see improvement. Your doctor will also order blood tests to check progress. Over time, your HbA1c (a measure of long-term blood sugar control) may also decrease.
• Weight Loss: While metformin isn’t used specifically for weight loss, some people see modest weight loss as metformin helps the body use glucose efficiently and reduces fat storage.³
• Lower Cholesterol: Metformin can help reduce LDL (“bad” cholesterol) and triglycerides, supporting better heart health.⁴
• Improved Ovulation and Menstrual Regulation: For people with PCOS, lower insulin levels from metformin can help stabilize androgens to improve menstrual cycle regularity.⁵

These changes might take some time, but they signal that metformin is positively impacting your body. 

How Much Does Metformin Lower A1C Levels?

Generally, an average metformin A1C reduction should be about 1 to 2 percent. The exact reduction varies between individuals and can depend on starting blood sugar levels, how well you adhere to your prescribed dosage, and whether you’re combining metformin treatment with a healthy diet and regular exercise.⁶ 

How Long Does Metformin ER Last?

Studies suggest that Metformin extended release (ER) lasts around 12 hours. Metformin peak time (highest blood levels) is four to eight hours after taking the extended-release tablets.⁷

How Long Does Metformin IR Last?

According to studies, Metformin immediate release (IR) lasts around six hours. The peak time for metformin IR is one to three hours.⁷

Signs Metformin Is Not Working

The primary sign that metformin isn’t working as it should is that your blood sugar remains high. You may notice this when you check your blood sugar at home or when your doctor orders follow-up blood work.

Some people aren’t aware their blood sugar remains high if they aren’t using glucose fingersticks or a continuous glucose monitor (CGM) to test. Still, over time, persistent high blood sugar (hyperglycemia) can lead to increased diabetes symptoms, including excessive thirst, needing to urinate more often, or increased hunger. Blurry vision, fatigue, or weight gain could also indicate issues with blood sugar.⁸

If your blood sugar won't go down with metformin despite taking it as prescribed, it may be a sign that the medication isn’t effectively controlling your blood sugar levels.  If you notice ongoing symptoms like excessive thirst, frequent urination, or increased fatigue, it’s essential to reach out to your doctor. They may recommend a higher dose of metformin, combining metformin with another medication, or exploring alternative treatments to help better manage your blood sugar. 

The most common side effects of metformin include stomach pain, nausea, diarrhea, and a metallic taste in the mouth. These usually aren’t serious and go away after a few weeks; however, contact your healthcare provider if they don’t improve or worsen.

What to Do if Metformin Is Not Working

Metformin may not be effective for everyone, and there are several reasons why this might happen. If blood sugar doesn’t go down with metformin, the dosage could be too low, or your body may not respond to the medication as expected. Sometimes, you might need a different medication to use alongside metformin or a completely new treatment to help lower your blood sugar levels.

If metformin isn’t working, your blood sugar can stay high, increasing the risk of serious complications. These may include high blood pressure (hypertension), heart disease, stroke, kidney disease, nerve damage (neuropathy), vision issues like diabetic retinopathy and glaucoma, or even cognitive decline.⁸

The good news is that your doctor and diabetes care team are there to support you. They can adjust your treatment plan, explore alternative options, and guide you toward the best solution for your body.  A healthcare professional may recommend a different medication if higher dosages do not change or worsen your symptoms. Common options include:

• Actos (Pioglitazone)
• DPP-41 Inhibitors: Januvia (sitagliptin), Tradjenta (linagliptin), Onglyza (saxagliptin), and Nesina (alogliptin)
• GLP1- Agonists: Bydureon (exenatide), Byetta (exenatide), Saxenda (liraglutide), Mounjaro (tirzepatide), and Adlyxin (lixisenatide)
• Injectable Insulin
• SGLT2 Inhibitors: Invokana (canagliflozin), Farxiga (dapagliflozin), Jardiance (empagliflozin), and Steglatro (ertugliflozin)
• Sulfonylureas: Amaryl (glimepiride), Glynase (glyburide), and Glucotrol (glipizide)

Your doctor will develop a treatment plan with you to reduce your blood sugar and prevent hypoglycemia (low blood sugar).

The Bottom Line

Metformin is an effective medication for managing type 2 diabetes. It helps lower blood sugar levels, improve insulin sensitivity, and even support other conditions like PCOS. The key to tracking progress is recognizing the signs that metformin is working, primarily improved blood sugar. 

If metformin isn’t working as expected, your healthcare team can help tailor your treatment plan to meet your needs. Combining medication with healthy lifestyle habits allows you to feel in control of your blood sugar.

Learn More About the Signos CGM Program

Signos incorporates cutting-edge research and the proven power of continuous glucose monitoring. The data gleaned from the Signos app can help guide your health journey. Not sure if Signos is right for you? Take this quiz to find out! Interested in learning more about nutrition and healthy eating habits? Check out more articles on our blog.