Foods to Avoid While Taking Metformin, According to a Pharmacist

Metformin is a commonly prescribed medication for managing type 2 diabetes, a chronic condition marked by high levels of glucose (sugar) in the blood. If not controlled, type 2 diabetes can cause serious complications such as vision problems (diabetic retinopathy), stroke, foot problems (ulcers and amputations), and coma.

Metformin helps lower glucose levels and improves hemoglobin A1C, a measurement of blood sugar control over time. A healthy diet optimizes the effectiveness of metformin and can help prevent complications of diabetes.

Foods to Avoid While Taking Metformin

Nutrition therapy is a crucial part of diabetes management. However, there’s no specific diet plan that works for everyone. Making a long-term individual food plan that you can commit to is essential.

For many people, the concept of everything in moderation is a helpful starting place. Most things are OK to eat in small amounts or occasionally. That said, the American Diabetes Association recommends avoiding the following foods when possible:

• Refined sugar: High-sugar foods and drinks like soda, candy, and baked goods increase blood sugar levels and may counteract metformin’s effectiveness. According to animal studies, even beverages sweetened with calorie-free sweeteners like saccharin may impair metformin’s effects on blood sugar. However, studies in humans are still necessary to confirm this finding.
• Refined carbohydrates: All carbohydrates (carbs) are broken down into glucose in the body. Refined carbohydrates like white bread, pasta, and pastries cause insulin and glucose levels to fluctuate, possibly leading to insulin resistance. This is when insulin doesn’t break down glucose efficiently, impacting glucose control.
• High-fat foods: These include fried foods, fatty cuts or types of meat, and some processed snacks. Excessive saturated fats can decrease insulin sensitivity, meaning the body doesn’t respond as well to insulin. In addition, high-fat foods keep the body from absorbing and using metformin efficiently. You may need a higher dose of metformin to control your blood sugar if you regularly eat high-fat foods. Keep in mind that not all fats are created equal. Some fats benefit people who take metformin, like monounsaturated fats (olive oil and nuts) and polyunsaturated fats (like fatty fish).
• Alcohol: Drinking alcohol while taking metformin may cause hypoglycemia (low blood sugar) and lactic acidosis (lactic acid build-up in the blood). Signs of lactic acidosis include fatigue, muscle pain, and stomach pain. If you have diabetes, drinking in moderation is key. Aim to limit alcoholic drinks to one per day for females or two for males if you’re taking metformin.
• Large amounts of specific fruits and vegetables: The glycemic index measures how quickly sugars are broken down in the body and enter the bloodstream. Fruits and vegetables with high glycemic indices cause a quick rise in blood sugar levels. These include watermelon and potatoes.

What Is Metformin?

Metformin (brand name Glucophage) is the first-choice medication prescribed for type 2 diabetes in adults and children who are at least ten years old. It’s available as an oral medication (taken by mouth) in immediate and extended-release formulations.

Metformin is also available in combination with other classes of diabetes medicines, including the following.

• Invokamet (canagliflozin and metformin)
• Janumet (metformin and sitagliptin)
• Kazano (alogliptin and metformin)

Metformin lowers blood sugar in the body through several different mechanisms, including the following:

• Blocking glucose production in the liver
• Increasing the effects of insulin, a hormone that breaks down glucose in the body
• Preventing glucose in the intestines from entering the bloodstream

Metformin has proved to help control blood sugar in people with diabetes for over 60 years. In addition, it’s taken off-label. Off-label means the U.S. Food and Drug Administration (FDA) hasn’t approved it for many other conditions, including the following:

What to Do if You Eat Foods You’re Trying to Avoid on Metformin

You might inevitably eat foods you’re trying to avoid from time to time while taking metformin. When this happens, keep the following tips in mind:

• Exercise: Exercise is beneficial for most people, including those with diabetes. Physical activity helps lower insulin resistance and control glucose levels. A single exercise session can help the body process glucose for up to three days, so it is a healthy starting point after overindulging. Consider walking with a friend or attending a group exercise class to reap social benefits as well.
• Hydrate: Be sure to sip water throughout the day to prevent dehydration. Metformin can build up in the body without proper hydration and cause side effects. Anytime you experience vomiting or diarrhea, whether from a rich meal, a night out, or otherwise, you’ll need to replenish with extra fluids.
• Adjust your metformin dose: Discuss with your healthcare provider whether you’ll need a higher dose of metformin if you have a high-fat or high-calorie meal. Eating these foods can make metformin less effective.
• Reach out to your network: If you’re having challenges, be sure to reach out to your healthcare or social support network.

Tips for Success

If you take metformin, consider the following tips to optimize its blood sugar-lowering effects.

• Eating a balanced diet: According to the American Diabetes Association (ADA) Consensus Report, many different diets can help manage diabetes. Eating a balanced diet with whole grains, lean protein, and non-starchy vegetables is essential.
• Portion control: Several techniques help people with diabetes manage their carbohydrate intake effectively. Common ones include portion control (eating smaller amounts), carb counting (tracking all the carbohydrates you eat or drink), and the plate method (certain food groups take up a specific percentage of your plate).
• Regular monitoring: Check your blood sugar regularly to assess how different foods affect your blood glucose levels.
• Stress management: Managing stress, attending to underlying mental health conditions, and building coping skills may help effectively manage your blood sugar and condition. Yoga and meditation may also help reduce your stress levels.
• Social support: Lean on your social support network or seek ways to grow it. Sources of social support include friends, family, neighbors, community organizations, and online communities.
• Medical nutrition therapy: Consider contacting your healthcare provider or registered dietitian nutritionist (RD/RDN) to help you evaluate your current dietary patterns, stress management, body composition, and other factors.

Other Considerations

Certain health conditions, medications, and medical procedures can impact the effects of metformin in the body. Some to keep in mind include:

• Specific conditions: Metformin is processed (broken down) by the kidneys. This means that if the kidneys aren’t working well, metformin builds up in the body. For this reason, people with kidney impairment should take a lower dose of metformin or a different medication altogether in some cases. Older people are also more likely to have increased metformin levels in the body, which can lead to an increased risk of side effects like lactic acidosis.
• Medication interactions: There are several drug interactions to keep in mind if you take metformin. Although metformin itself is unlikely to cause hypoglycemia, taking it with other diabetes medicines, including insulin, can make blood sugar levels drop. On the other hand, medicines that can increase blood sugar will make metformin less effective. A few examples are corticosteroids, diuretics (water pills), and birth control pills. Lastly, taking a class of medicines called carbonic anhydrase inhibitors with metformin increases the risk of lactic acidosis. These medicines include Topamax (topiramate) and Zonegran (zonisamide).
• Specific procedures: If you have a scheduled surgery, you’ll likely stop taking metformin temporarily to minimize risks of low blood pressure and kidney problems. In addition, you may need to temporarily stop taking metformin if you are having imaging contrast or during an acute illness.
• Nutrition interactions: Metformin can lower the levels of vitamin B12 in the body. Ask your healthcare provider if B12 supplements are right for you. In addition, some dietary supplements may enhance the effects of metformin and cause hypoglycemia. Examples include chromium, zinc, fenugreek, cinnamon, and ginger. Do keep in mind that more data is necessary to determine the effects of these or other supplements on blood sugar. Discuss the supplements you take with your healthcare provider for optimal safety.

Summary

Metformin is a common medication for managing type 2 diabetes. It is most effective when combined with dietary changes, such as limiting refined sugars, high-fat foods, and alcohol.

Lifestyle modifications are an essential part of managing diabetes. In addition to a healthy diet, these include exercise, hydration, and regular glucose monitoring.