Signs metformin is working

In this article:

• Metformin uses
• Signs that it's working
• Results timeline
• Signs that it's not working

In this article

• Metformin uses
• Signs that it's working
• Results timeline
• Signs that it's not working

Metformin (brand names Glucophage and Riomet) is a generic prescription drug approved by the U.S. Food and Drug Administration (FDA) to treat Type 2 diabetes mellitus. The oral medication works by improving your body’s insulin sensitivity and reducing the liver’s glucose production. Like any medication, there are certain signs, both noticeable and not as apparent, that can let you and your healthcare provider know if metformin is working, or if you need to explore other treatment options.

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Metformin uses

Metformin is only FDA-approved to treat Type 2 diabetes. 

“It is usually started as the first-line drug for a new diagnosis when blood glucose cannot be maintained with diet and exercise only,” says Victoria Finn, MD, an endocrinologist with Medical Offices of Manhattan, in New York, and contributor to Lab Finder. 

While its only indication is for Type 2 diabetes, Dr. Finn notes that healthcare providers may prescribe metformin off-label for other conditions linked to insulin resistance. These conditions include prediabetes, gestational diabetes, and polycystic ovary syndrome (PCOS). In some cases, it may also be incorporated into a medical weight-loss plan.

Dr. Finn explains that metformin works by reducing the amount of glucose produced by the liver while increasing insulin sensitivity in muscles and other tissues. “As a result, glucose is used more efficiently,” she says. “In Type 2 diabetes, this leads to lower blood sugar levels.” Because metformin improves the body’s response to insulin, it may also benefit people with prediabetes and gestational diabetes.

Metformin’s effects on insulin regulation can also be helpful for people with PCOS. According to James J. Chao, MD, FACS, a board-certified plastic surgeon and weight-loss specialist, the use of metformin for PCOS can help an irregular menstrual cycle return to normal. “In the case of PCOS, where insulin spikes lead the ovaries to overproduce androgen, metformin disrupts that cycle and can help restore the menstrual cycle,” he explains.

Signs that metformin is working

Signs that indicate that metformin is working correctly in your body include:

• Better blood sugar levels
• Reduced symptoms of high blood sugar:
  • Less frequent urination
  • Reduced excessive thirst
  • Less brain fog
  • Better vision
  • Fewer headaches
  • Improved wound healing
  • Reduced dry mouth and skin
• Changes in body weight and appetite
• Improved energy levels
• Regular menstrual cycle

These signs can occur gradually and can vary based on the medical condition being treated, dosage, and individual response.

Blood tests that show metformin is working

Healthcare providers can often tell metformin is working by looking at improvements in blood sugar-related lab results. One of the earliest and most noticeable changes is a drop in fasting blood glucose. 

“I typically know it’s working when I see lower fasting blood glucose,” Dr. Chao says. “We’re talking pre-breakfast numbers that used to be over 130 mg/dL, and then come down to under 100 mg/dL in a matter of weeks.” Research supports this effect, showing that metformin can reduce fasting plasma glucose concentration and glucose production by 25% to 35%. 

Improved hemoglobin A1c (HbA1c) is one of the most important signs that metformin is working, according to Dr. Finn. “This is a key marker that reflects the average blood glucose level over a period of three months,” she says. Dr. Chao adds that a reduction in A1c of about 0.5% to 1.5% within three months is strong evidence that the medication is working. One study found that taking metformin glycinate for 2 months led to a greater decrease in A1c levels than a placebo in people with Type 2 diabetes.

Metformin can also improve post-meal blood sugar control and reduce episodes of extreme highs and lows. “Due to more stable glucose levels, patients experience fewer post-meal glucose crashes, less blood glucose fluctuation, and improved energy throughout the day,” Dr. Finn says. Dr. Chao adds that this stabilization can also help reduce mental fog around mealtimes for people with Type 2 diabetes. Oral glucose tolerance tests (OGTTs) and continuous glucose monitor (CGM) data can be especially useful for identifying these improvements, as they show how blood sugar responds after eating. 

Beyond glucose levels alone, improvements in insulin sensitivity can also be reflected in lab results. Lower fasting insulin levels, improved HOMA-IR scores (an insulin resistance test), and physical changes such as reduced waist circumference or fading acanthosis nigricans (dry, dark patches that may appear in skin creases such as the armpits, neck, or groin) may all signal better insulin resistance. Dr. Finn also notes that triglyceride levels may decline as blood sugar improves, since the liver converts excess glucose into triglycerides when blood sugar is high.

For people with PCOS, metformin’s hormonal and metabolic effects can also be reflected in lab results. Research shows that a six-month regimen of 1,000 to 2,000 mg of metformin improved several markers, including HOMA-IR, homocysteine, blood pressure, lipid profiles, and C-reactive protein (CRP), indicating improvements in insulin resistance, inflammation, and cardiovascular risk factors.

Throughout treatment, kidney and liver function are routinely monitored, as impaired renal function can increase the risk of rare but serious side effects such as lactic acidosis. 

Overall, Dr. Finn says that tracking trends, especially through HbA1c results and CGM data, provides the clearest picture of how well metformin is working over time.

Improved physical symptoms

Taking metformin for diabetes-related medical conditions can also lead to physical changes. Polydipsia, or excessive thirst and fluid intake, is a common symptom of diabetes mellitus and diabetes insipidus, and often leads to dry mouth and frequent urination, particularly at night. Taking metformin can help lower high blood sugar levels and, over time, reduce excess thirst, dry mouth, and frequent urination.

Appetite changes and weight loss

Significant indicators that metformin is working include changes in appetite and weight. “Many patients notice appetite reduction and fewer cravings.” Dr. Finn says. “As a result, mild weight loss may be observed.”

Metformin can decrease hunger and increase feelings of fullness, leading to reduced calorie intake and possible weight loss. Research shows that metformin increases blood levels of the appetite-suppressing metabolite N-lactoyl phenylalanine (Lac-Phe). Because metformin boosts this natural “anti-hunger” metabolite, people with Type 2 diabetes tend to have reduced cravings for sugar and carbohydrates while taking the medication. 

The antidiabetic drug can also significantly affect a person’s body composition. One study found that metformin treatment in women with prediabetes or insulin resistance led to a decrease in body mass index (BMI) and waist circumference.

Improved PCOS symptoms

Metformin can help address menstrual cycle irregularities in people with PCOS. “In conditions like polycystic ovary syndrome, improved insulin sensitivity lowers androgen production by the ovaries,” Dr. Finn explains. “That helps restore regular ovulation and menstrual cycles.”

Because metformin’s mechanism of action can restore regular ovulation and menstrual cycles, research shows that the medication can also help treat PCOS-related infertility.

Another benefit of metformin for PCOS is that its effect on hyperandrogenism (high androgen levels) can help reduce excess hair growth (hirsutism) and acne – two common symptoms of the hormonal condition. According to research, a year-long metformin treatment led to a significant reduction in hirsutism in people with PCOS between the ages of 20 and 40 years old. In another study, researchers found that using metformin led to a significant improvement in acne for people with PCOS.

How long does it take to see the results of metformin?

Metformin can begin to take effect within the first 10 days, Dr. Chao says. However, it can take up to two months to get the full benefits of the medication.

Here’s a quick breakdown of the timeline:

Signs that metformin is not working

There are instances where taking metformin may not improve symptoms of Type 2 diabetes, prediabetes, gestational diabetes, or PCOS. Signs that metformin is not working include persistent high blood sugar levels, blurred vision, increased thirst or hunger, frequent urination, headache, fatigue, weight loss, and others. If you’re not seeing improvement in your health, please contact your healthcare provider for medical advice and to explore other treatment options.