How long does metformin take to work?

Key Points

• Metformin will usually start lowering your blood sugar (glucose) levels in the first week of treatment, but it may take 2 to 3 months to see its full effect.
• Metformin is a preferred initial oral treatment for people with type 2 diabetes, and is usually taken on a long-term basis.
• It may be combined with other blood glucose-lowering treatments, if needed, and as prescribed by your doctor.

In a Phase 3 study in 706 patients, both the immediate-release and extended-release oral tablet forms of metformin were evaluated for effectiveness. Results showed rapid decreases in fasting plasma glucose (FPG) levels by the end of the first week. FPG levels continued to decline until week 8, and lower blood glucose levels were maintained for the duration of the 24-week long study.

Metformin is used with diet and exercise and is approved by the FDA for blood sugar control in the treatment of type 2 diabetes in adults and children 10 years of age and older. Metformin may be used in combination with insulin or other type 2 diabetes medications to help control blood sugar levels.

Metformin is usually taken with meals, either once or twice a day. It comes in immediate-release tablets of 500 mg, 850 mg, and 1000 mg and extended-release tablets of 500 mg and 750 mg, as well as an oral solution.

What are the signs that metformin is working?

The signs that metformin may be working for you include:

• lower blood sugar levels after eating, if you test at home
• lower HbA1c levels (which measure long-term control)
• modest weight loss, or typically no weight gain (metformin should be used with a healthy diet and regular exercise)

Your healthcare provider will also monitor your blood sugar control by looking at results from your hemoglobin A1c (HbA1c) test, usually every 3 to 6 months. This is one of the best ways to determine if metformin is working for you over the long-term. A typical goal A1C is ≤7%, but based on specific factors your goal A1C may be lower or higher, as recommended by your doctor.

A hemoglobin A1c (HbA1c) test is done by a simple blood test in your doctor's office or a lab using a small amount of blood from a finger stick or from your arm. You don't need to fast to prepare for your A1C test, and can have it at any time of the day. Ask your doctor if you need to fast for other tests that may be done at the same time.

In one double-blind study looking at both immediate-release and extended-release forms of metformin, significant decreases in HbA1c (A1C) levels were seen by week 12 in all treatment groups.

• The A1C mean changes in those given 1,500 mg extended-release metformin once or twice daily (−0.73 and −0.74%) were not different from those given the 1,500 immediate-release tablets twice daily (−0.70%).
• The group receiving the 2,000 mg extended-release tablet daily had a greater decrease in A1C levels (−1.06%).
• Blood sugar control was continuous throughout the 24 week long study.

Related Questions

• When is the best time to take metformin?
• What is the safest diabetes medication?
• Why does metformin cause diarrhea?

How much will metformin lower A1C / blood sugar?

When metformin is used as a single drug treatment (without other diabetes treatments like insulin), it will typically lower your A1C by about 1% to 2% on average.

A1C is a measure of long-term blood sugar control. In most patients, metformin is suggested as the initial treatment for type 2 diabetes, but its glucose-lowering effect may not be adequate for all patients when used alone, especially over time.

• In metformin clinical studies, obese patients with type 2 diabetes with high blood sugar not controlled by diet alone were started on metformin or a placebo (a pill that contains no medicine)
• Patients received metformin hydrochloride (up to 2,550 mg/day) or a placebo
• After about 7 months, the average A1C was 7.1% in the people who took metformin and 8.6% in the people who took the placebo pill, an A1C reduction of 1.5%.

If needed, other type 2 diabetes treatments can be combined with metformin, including:

• insuli
• oral sulfonylureas (for example: glipizide, glyburide, glimepiride)
• glucagon-like peptide 1 (GLP-1) receptor agonists
• sodium-glucose co-transporter 2 (SGLT2) inhibitors
• dipeptidyl peptidase 4 (DPP-4) inhibitors
• repaglinide
• pioglitazone

Why is metformin usually the first treatment for type 2 diabetes?

Metformin is often used as the first treatment in type 2 diabetes because of its:

• ability to control blood sugar levels
• low risk of weight gain
• low risk of hypoglycemia (low blood sugar)
• availability as an affordable oral tablet
• long history of safety and effectiveness

This is not all the information you need to know about metformin for safe and effective use and does not take the place of your health care provider’s directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.