How Long Does Metformin Take to Work? 6 Signs to Look For

People trying to manage their type 2 diabetes with medication may be prescribed to try metformin to improve their health condition. Metformin is an antidiabetic agent that people have been taking since 1994, and many health professionals still prescribe metformin as part of a diabetes care plan.¹

Currently, the American Diabetes Association recommends metformin for people who have:

• Prediabetes between the ages of 25 and 59
• An HbA1c of 6% or higher
• A BMI of 35 or higher
• A fasting plasma glucose of 110 mg/dL or higher
• A prior gestational diabetes diagnosis
• A type 2 diabetes diagnosis

Learn more about how this drug works to better discuss your options with your primary care physician.

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How Long Does It Take for Metformin to Work?

At its core, Metformin reduces the amount of sugar that 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

The human body needs time to work alongside metformin’s active ingredients. These ingredients train the liver to reduce its average glucose production while increasing the body’s insulin sensitivity. Both significant changes take time, especially if the patient has a severe case of diabetes.

6 Signs Metformin Is Working

You might wonder how metformin works and how it could positively impact your daily life. Below are six signs that indicate metformin is working as intended to reduce hyperglycemia symptoms.

1. Balanced Blood Sugar Levels

Experts recommend checking your blood sugar levels four times daily if you live with diabetes.³ Continuing blood tests after beginning a metformin prescription should reveal better balance within a few days.

Metformin lowers blood glucose levels more effectively with time because it teaches your body a different way to respond to glucose. Drastic spikes will become less common as weeks and months pass.

2. More Energy

Metformin will give you energy once your blood sugar levels become stable long-term. Your body can absorb glucose effectively, providing more sugar-based power to your mind and organs. The extra energy can also reduce your risk of cancer by energizing your cells to fight cancer-causing free radicals in your bloodstream.

3. Glycemic Control

Gaining more power over high blood sugar spikes will improve glycemic control. Metformin improves the body’s ability to regain this essential ability, leading to balanced natural glucose-insulin administration.

4. Weight Loss Management

Slight to moderate weight loss is one of the signs that metformin is working. As your body processes sugar more effectively, it stores less sugar in fat cells. This side effect is encouraging for people who are obese or who may have gained weight on other medications.

5. Less Frequent Bathroom Trips

When your body can’t process glucose properly due to a diabetes diagnosis, your blood contains more glucose. Your kidneys produce more urine to flush the sugar out of your body, driving your desire to drink more beverages.

One of the side effects of metformin is less frequent urination. The reduced glucose in your blood means less urine production, making you feel less thirsty.

6. Not Feeling as Hungry

If your organs aren’t getting energy through processed glucose, your brain will signal a need for more food. Although it may take a few days for metformin to work, you’ll know it’s working when you naturally feel less hungry. Your body will turn glucose into energy more effectively, reducing your need to eat as often.

6 Signs Metformin Is Not Working

Metformin does come with the risk of possible side effects, but this is not an indication that the medication is not working. If you experience any of the below side effects and they get worse or do not go away after a few weeks, consult your healthcare provider.

• Nausea
• Vomiting
• Diarrhea
• Decrease appetite
• Weight loss
• A metallic taste in your mouth
• Heartburn
• Bloating
• Constipation
• Stomach pain

Below, we dive deeper into some signs that metformin may not be working properly within your body. Talk with your doctor if you notice any of these symptoms affecting your quality of life.

1. Blood Sugar Spikes

Patients on metformin aim to balance their blood sugar spikes and increase blood sugar control. If you’re following a low-to-no-sugar diet and incorporating daily physical activity into your routine but still noticing blood sugar spikes in the days or weeks after beginning your prescription, talk with your doctor about your concern.

2. Fatigue

Metformin gives you energy when it successfully teaches your body how to convert glucose. If you experience fatigue after starting your prescription, it could indicate that it isn’t working as your doctor intended.

3. Hunger

Feeling hungry more often than not means your body isn’t getting energy from glucose. If you're concerned, discuss this side effect with your doctor. Eating more than usual may indicate that metformin or your current dosage isn’t right for your body.

4. Weight Gain

People often report weight loss when taking metformin. If you gain weight despite keeping your diet and exercise routine the same, it could mean that your glucose sensitivity has remained.

5. Headaches

Low blood sugar tightens blood vessel dilation while increasing blood flow to the brain.⁴ Metformin should produce fewer headaches, so call your doctor if you’re experiencing the same amount or more a few days or weeks after beginning your dosage.

6. Increased Thirst

When you start taking metformin, it should decrease your thirst by improving your glucose absorption. Drinking more beverages than usual is a sign the medication isn’t working as intended.

What if Metformin Is Not Working?

Your first dosage of metformin may not work because it’s too low. Your doctor might increase your dosage once or twice to find the best amount for your body. Your doctor can also discuss other treatment options depending on your health history. It’s not a bad sign if metformin doesn’t work for you. It only means other avenues are better solutions.

What to Do if Metformin Has Stopped Working

Metformin is often prescribed after lifestyle changes or interventions, like diet, regular exercise, and weight loss, are recommended. If metformin is unable to control blood sugar levels, this could lead to an excessive accumulation of glucose in the bloodstream and cause possible complications such as high blood pressure (hypertension), coronary artery disease, peripheral artery disease, stroke, chronic kidney disease, diabetic retinopathy, diabetic neuropathy, glaucoma, and/or cataracts.

If metformin has stopped working, your doctor may increase your medication dosage. Beginning on a lower dose and giving it a few weeks to take effect may be beneficial before increasing your prescription strength.

If higher dosages do not change or worsen your symptoms, your primary care provider may recommend a different medication. Common options include:

• Actos (Pioglitazone)
• DPP-41 Inhibitors: Januvia (sitagliptin), Tradjenta (linagliptin), Onglyza (saxagliptin), and Nesina (alogliptin) 
• GLP1- Agonsits: 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 may also recommend other treatment options if metformin or other medications aren’t in your best interest. Insulin therapy can help in 30 minutes or less, while incretin-based therapies can help after meals.

Frequently Asked Questions

These are the most frequently asked questions about metformin. Consider the answers before discussing what’s best for you with your doctor.

What Happens if You Take Metformin and Don’t Need It?

If you take metformin and don’t need it, you’ll block your body’s absorption of vitamin B12.⁵ This essential mineral prevents anemia, so taking it may increase your risk of low red blood cells. 

Some people think it could extend your life span if you do not live with diabetes, but research from Frontiers in Endocrinology doesn’t support that theory.⁶ Given how it’s only available through a prescription, it isn’t likely you’ll access metformin without a diabetes diagnosis.

How Often Should You Check Blood Sugar on Metformin?

The side effects of taking metformin as your doctor prescribes start within a few days. You should continue checking your blood sugar at least four times daily or at the same frequency you needed before taking metformin.

When Should Metformin Be Taken?

Starting metformin requires timing your dosages correctly. The oral tablet may need to accompany a meal twice or thrice daily, while the liquid form may only require two daily doses alongside two meals or snacks.

Discuss your dietary options with your doctor if you’re unsure what to eat or drink with your prescription. They’ll caution against combining it with things like alcoholic beverages, which increase your lactic acidosis chances by causing more buildup in the liver.

What Are Metformin Alternatives?

If metformin doesn't work, your healthcare provider may recommend other diabetes medications. Other options include Ozempic or Jardiance. Both help people manage their blood sugar levels.

What if I Miss a Dose of Metformin?

If you miss a metformin dose and notice it within a few hours, take it with food as normal. If it’s closer to the time of your next dose, take it as usual to avoid doubling up.⁷ 

Avoid taking some vitamins and supplements while waiting for your metformin results. The medication interacts negatively with things like St. John’s wort and prickly pear cactus extract. Substituting them for a missed metformin dose could result in digestive upset or drastic changes in blood sugar readings.

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.