6 Foods You Should Avoid While Taking Metformin

Optimize the benefits of metformin by avoiding certain foods. Discover lifestyle habits to promote blood sugar control alongside metformin.

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Science-based and reviewed

April 23, 2024
September 17, 2023
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Metformin is one of the most well-known diabetes medications used to treat type 2 diabetes

Although Metformin is approved for treating type 2 diabetes, it is also used off-label to treat polycystic ovarian syndrome (PCOS), infertility, prediabetes, pregnancy complication prevention, and obesity.

If you are one of the many who rely on this medication or are considering its use, it’s important to understand how metformin works and how a nutritious diet can complement its effectiveness.


Understanding How Metformin Works

Let’s look at how metformin works to lower blood sugar levels and why it is so effective in treating diabetes.

Enhanced Insulin Sensitivity

Metformin works mainly by making the body more sensitive to insulin. In diabetes, particularly type 2 diabetes, the body's cells become resistant to the effects of insulin. As a result, glucose (sugar) in the bloodstream cannot efficiently enter the cells to be used for energy, leading to elevated blood sugar levels. Metformin intervenes by making these cells more receptive to insulin's signals, which allows glucose to enter the cell and be used for energy.1

Reduced Glucose Production

Another important way that metformin helps treat diabetes is by reducing the amount of glucose produced in the liver. The liver plays a key role in regulating blood sugar levels by releasing glucose into the bloodstream when needed. In individuals with diabetes, the liver often overproduces glucose, leading to spikes in blood sugar levels. Metformin curbs this excess glucose production, promoting blood sugar that remains within a healthy range.1

Improved Muscle Glucose Uptake

Metformin further aids in diabetes management by enhancing the uptake of glucose by muscle cells. Muscles are significant users of glucose in the body. When they can efficiently take up glucose, it lowers blood sugar levels and increases overall energy utilization, promoting energy balance and improving overall health.1

Metformin is a reliable foundation for managing the condition, primarily because it improves insulin resistance and reduces hyperglycemia. However, metformin is not a magic bullet. While it does an impressive job of keeping blood sugar levels within healthy ranges, it is not a bandaid for poor dietary choices. 

Metformin can still work to lower blood sugar levels even if you occasionally indulge in foods that can spike your blood sugar. However, your medication won't be as effective if you regularly eat high-glycemic-index foods or large portions of carbohydrates without balanced meals. Making healthy food choices is still important to achieve the best possible results.

6 Foods to Avoid and Reasons Why

While metformin can help manage blood sugar, dietary choices can significantly impact its effectiveness. Here are some specific foods that individuals taking metformin should consider avoiding or consuming in moderation:

  1. Alcohol

Alcohol can be combined with metformin in moderation, but it’s even better to avoid it altogether. Taking metformin and drinking alcohol can increase the risk of lactic acidosis, a condition characterized by the buildup of lactic acid in the liver, which can lead to kidney failure and damage to the lungs and heart.2 

Alcohol may also cause digestive discomfort in some individuals, and alcohol may increase these symptoms. 

  1. Saturated Fats

While some healthy fats can support heart and brain health, consuming too many high-fat foods can harm your health. 

Foods high in saturated fats, such as fatty cuts of meat, fried foods, and full-fat dairy products, can reduce insulin sensitivity when eaten in excess. Since metformin enhances insulin sensitivity, a diet rich in saturated fats can counteract its effects, making it less efficient in controlling blood sugar levels.

  1. Refined and Simple Carbs

Refined carbohydrates like white bread, white rice, sugary cereals, and pastries can cause rapid spikes in blood sugar. Metformin's ability to regulate these spikes can be overwhelmed by a diet high in simple sugars and refined carbs. 

Strive to eat more complex carbohydrates that provide a steady energy source and are more compatible with metformin therapy.

  1. Too Much Fiber

While high-fiber foods are generally beneficial for diabetes management because they slow digestion and the release of glucose into the bloodstream, consuming them in excess alongside metformin can interfere with how your body absorbs the medication. 

Do not take fiber supplements or simultaneously eat high-fiber foods – such as avocado, berries, beans, chia seeds, chickpeas, and oatmeal – as your medications. It’s best to wait a few hours in between. You should talk to your doctor before taking fiber supplements if you have diabetes and are taking metformin.

  1. Too Much Sodium

Although salt does not affect blood glucose levels, it's important to limit the amount you consume as part of your diabetes management regimen because too much salt can result in high blood pressure.

Hypertension often occurs in people who have diabetes mellitus, so eating a low-sodium diet can help with blood pressure management. 

  1. Highly Processed Foods

Highly processed foods often contain hidden sugars, saturated and trans fats, and additives that may disrupt blood sugar control. These foods can also contribute to weight gain, a risk factor for insulin resistance. To optimize the effectiveness of metformin, prioritize whole, unprocessed foods and home-cooked meals most of the time.

Work with a registered dietitian or certified diabetes educator to develop a personalized nutrition plan that supports nutrition needs and increases the efficacy of your medication regimen.

A Diabetes-Friendly Diet: What Should You Eat?

Eating a healthy diet is an important part of any diabetes management program. So what does a diabetes-friendly diet look like, you ask? 

A diabetes-friendly diet is rich in whole, nutrient-dense foods, including fruits, vegetables, whole grains, legumes, lean protein, and healthy fats. It is also low in saturated fat, added sugar, and sodium. 

Here are some foods to include to manage your blood sugar levels:

  • Complex Carbohydrates - These complex carbs are digested more slowly, leading to more stable blood sugar levels.
  • Whole grains like brown rice, quinoa, whole wheat pasta, whole grain bread, oatmeal, lentils, sweet potatoes, pumpkin
  • Healthy Fats - These fats provide essential nutrients, help improve insulin sensitivity, and fight heart disease.
  • Avocados, nuts, seeds, salmon, and olive oil
  • Fiber - Fiber helps stabilize blood sugar levels and promotes digestive and heart health. Be careful not to eat too much fiber, and avoid eating it at the same time as you take metformin.
  • Vegetables, leafy greens, legumes (beans, lentils), and whole fruits (with skin)
  • Non-Starchy Vegetables - These vegetables are low in carbohydrates and calories but high in essential nutrients.
  • Broccoli, spinach, kale, bell peppers, zucchini, asparagus, cabbage, artichokes, tomatoes, cauliflower, celery
  • Lean Proteins - Protein helps with satiety and doesn't significantly affect blood sugar levels.
  • Chicken breast, lean ground turkey, extra lean ground beef, ground venison, fish, tuna, tofu, beans, lentils, eggs, non-fat dairy (Greek yogurt, cottage cheese, milk)

A healthy diet is key to achieving better blood sugar control while taking metformin. Here's why:

Stabilizing Blood Sugar

Metformin helps regulate blood sugar levels but is most effective when paired with a consistent and balanced diet. Complex carbohydrates, lean proteins, and healthy fats work together to provide sustained energy and minimize blood sugar spikes.

Managing Carbohydrate Intake

Carbohydrates have the most significant impact on blood sugar levels. Managing your carbohydrate intake and choosing complex carbs over simple ones can lead to better blood sugar control.

Satiety and Weight Management

A balanced diet also promotes feelings of fullness and can aid in weight loss. Maintaining a healthy weight is crucial for diabetes management as it can improve insulin sensitivity and overall health.

Optimizing Your Metformin Regimen

Taking metformin as part of your diabetes management plan can be highly effective, but not without other lifestyle considerations. Here's our expert advice on how to get the most out of your metformin regimen:

1. Follow Your Healthcare Provider's Guidance

Always follow the dosing instructions provided by your healthcare provider. Metformin comes in different formulations, including an immediate-release and extended-release tablet. The dosing and timing can vary, so following your prescriber’s recommendations is important.

2. Timing Matters

Regular vs. Extended-Release

Depending on the type of metformin prescribed, the timing of your doses may differ. Regular metformin is usually taken with meals, while extended-release metformin is often taken once daily with an evening meal. Follow your healthcare provider's instructions to ensure optimal blood sugar control.


Try to take your metformin at the same time each day. Consistency helps maintain steady medication levels in your body, making it more effective at managing high blood sugar. 

3. Gradual Dose Escalation

The medication is often prescribed at a lower dose initially, which is gradually increased to minimize the side effects of metformin. This approach allows your body to adapt to the medication and reduces the risk of gastrointestinal discomfort.

4. Monitor Blood Sugar Levels

Regularly monitor your blood sugar levels as advised by your healthcare provider. This helps you and your provider gauge how well metformin works for you. Adjustments to your medication or diet plan can be made based on these readings if necessary.

5. Addressing Side Effects

Gastrointestinal Upset

When starting metformin, gastrointestinal side effects like diarrhea, nausea, or abdominal discomfort can occur. These often subside as your body gets used to the medication. If side effects persist or worsen, consult your healthcare provider, as they may adjust your dosage or recommend different formulations.

Vitamin B12 and Folate

Long-term metformin use has been associated with lower vitamin B12 and folate levels. Your healthcare provider may recommend regular monitoring of these levels and, if necessary, supplementation.

6. Diet and Lifestyle

Balanced Diet

As discussed earlier, a healthy diet is important in managing diabetes alongside metformin. Consult a registered dietitian to create a personalized meal plan that aligns with your metformin therapy.


Regular physical activity can improve insulin sensitivity, prevent heart disease, and enhance the effects of metformin. Discuss an exercise plan with your healthcare provider.

7. Consult Your Healthcare Provider

Before changing your medication or diet, consult your healthcare provider. Communication with your provider is essential for managing diabetes effectively.

Remember that metformin is just one aspect of diabetes management, and a holistic approach that includes medication, diet, exercise, and regular glucose monitoring is the best way to achieve better blood sugar control and overall health.

Learn More About the Impact of Blood Sugar on Overall Health with Signos’ Expert Advice

Signos CGM is a great tool for managing diabetes. It allows you to keep track of your blood sugar throughout the day and see how different foods affect your blood sugar. It can also show you how nutrition and exercise impact your blood sugar. 

Signos CGM empowers you to improve your health by keeping track of your diet, exercise, sleep habits, and blood sugar. Knowledge is power, and a CGM can give you specific information about how your habits affect your health. 

Signos has a team of health experts who compile evidence-based nutrition information to help you improve your health and wellness. Check out the resources here.

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Topics discussed in this article:


  1. Rena, G., Hardie, D. G., & Pearson, E. R. (2017). The mechanisms of action of metformin. Diabetologia, 60(9), 1577–1585. https://doi.org/10.1007/s00125-017-4342-z
  2. Takayama, K., Obata, Y., Maruo, Y., Yamaguchi, H., Kosugi, M., Irie, Y., Hazama, Y., & Yasuda, T. (2022). Metformin-associated Lactic Acidosis with Hypoglycemia during the COVID-19 Pandemic. Internal medicine (Tokyo, Japan), 61(15), 2333–2337. https://doi.org/10.2169/internalmedicine.9179-21
  3. Recipes & Nutrition. Recipes & Nutrition | ADA. (n.d.). https://diabetes.org/healthy-living/recipes-nutrition

About the author

Victoria Whittington earned her Bachelor of Science in Food and Nutrition from the University of Alabama and has over 10 years of experience in the health and fitness industry.

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