Foods to avoid while taking metformin

At this point in your weight care journey, you’ve probably heard of metformin—and know that studies have found it effective for weight loss. But, you may be questioning if there are any specific eating habits you should change or adhere to while taking it. Here’s where we come in—your Found health care provider can help educate you on foods to avoid while taking metformin, ways to eat a more nutritious diet, and any interactions that could occur. 

Here’s a little history: metformin’s been around for more than 60 years—it’s one of the most common diabetes medications in the world. And while the Food and Drug Administration (FDA) approved metformin to treat type 2 diabetes, it has also been proven effective in treating other diseases, including obesity and polycystic ovary syndrome (PCOS). There’s even research that suggests it may even reduce the risk of certain cancers. 

While metformin isn’t a cure for type 2 diabetes, it is an effective treatment. It’s used in diabetes management to lower blood glucose levels so the body can regulate insulin levels. Because of its ability to lower blood sugar levels, it can help as a weight management tool in your weight loss journey. 

Your Found health care provider will determine if metformin for weight loss is right for you and discuss side effects or other potential interactions with the medication—including foods, beverages, or other drugs. Any medical advice you receive should be from a licensed health care provider. Here’s what you need to know about foods to avoid while taking metformin.

Foods to avoid while taking metformin

For the most part, you're safe to eat most foods while taking metformin. However, there are some foods to avoid while taking metformin for various reasons. We’ll highlight these foods below to help you enjoy the most success in your weight loss journey. 

Some simple and refined carbohydrates

Metformin helps limit blood glucose levels. Simple and refined carbs boost those blood sugar levels, which can increase weight gain and cause metformin not to work as well as it should. Foods like white bread, white pasta, and most chips, crackers, and cookies have little fiber and lots of sugar. 

Look at labels, and steer clear of candy, soda, and super-sugary desserts as much as possible. Eating foods that raise your blood sugar won’t stop metformin from working, but it will make it more challenging for it to do its job, so these are some foods to avoid while taking metformin.

Eat saturated fats in moderation

While metformin is a diabetes drug, it’s also used off-label to treat obesity. Saturated fats can increase inflammation and make it harder to lose weight. So even as metformin works to help you lose weight, saturated fats can counter that effort and make it tougher for it to perform optimally. 

Red meat and dairy products—like milk, cheese, and butter—are popular sources of saturated fats. These aren’t foods to avoid while taking metformin altogether but focus on lean proteins—like turkey, fish, and tofu to increase metformin’s efficacy.

Avoid trans fat

Trans fat can happen naturally in some foods and be added to others. It raises cholesterol, causes inflammation, and increases the risk of heart disease. Baked goods and fast and fried foods can all contain trans fat, making these foods to avoid while taking metformin. So be on the lookout for it by checking nutritional labels when buying groceries or eating out.

Limit sodium

Those with obesity also often have high blood pressure or heart problems. Excessive amounts of salt may increase the risk of those other conditions and lead to more life-threatening issues. The FDA recommends consuming less than 2,300 mg of sodium per day—that’s about one teaspoon of table salt—and most Americans consume about one and a half times that. 

In a clinical review of studies published in Clinical Nutrition Research, researchers noted that a Korean study showed that a “low-sodium diet could improve not only blood pressure, but also the level of fasting blood glucose and insulin resistance.” Metformin works to help with lowering blood glucose, so you’re increasing its efficacy when you maintain a low-sodium diet.

Our bodies need salt to function, but too much salt is harmful. So again, look at packaged and prepared food labels when you shop. The FDA also warns common sources of sodium can be foods we may not even think to have it, like cereal, condiments, and pastries. Always check the nutrition facts and remember those with high sodium content are foods to avoid while taking metformin.

What foods trigger metformin side effects?

metformin side effects are typically mild and can include nausea, upset stomach, or diarrhea. Foods that may trigger or increase those symptoms are best not to eat—like high-fat, sugary, or fried foods. These often contain trans fat, are served in larger portions at restaurants, and have tons of added sodium. 

A study published in 2014 in the American Journal of Clinical Nutrition analyzed the association between fried food consumption and type 2 diabetes. Researchers found eating fried foods increases the risk of developing type 2 diabetes—the exact disease metformin is FDA approved to treat.

Another food to mention, because there’s been some chatter suggesting it may interfere with metformin, is grapefruit. While animal studies suggest grapefruit and grapefruit juice may interact with metformin, human studies have not shown the same interaction. Ultimately, the FDA doesn’t mention grapefruit as one of the foods to avoid while taking metformin. 

What is the best diet while taking metformin?

Some foods that help support how well metformin will work in your body and assist in your weight loss journey. Here’s what we found:

Eat complex carbs

Brown rice, whole-grain bread, oatmeal, and quinoa all contain complex carbohydrates. These take longer for the body to digest, causing blood glucose levels to rise steadily, maintaining healthy insulin levels. One way metformin may help lower blood glucose levels is by changing gut microbiota (the billions of microorganisms in your gut that help regulate your health and wellness). 

Additionally, a 2017 study in Frontiers of Nutrition found foods with complex carbs can help support weight loss because they “alter the composition of the gut microbiota,” leading to the best use of these “prebiotics,”' and that may help to treat obesity. So, think of it like this: Metformin is co-piloting with complex carbs in your body to give you the healthiest gut, leading to more sustainable weight loss when taken together. 

In addition, complex carbs also help you feel full longer as your body digests them, causing your blood sugar levels to increase more gradually. 

Stick to healthy fats

A diet high in foods like “olive oil, avocados, almonds, peanuts, macadamia nuts or hazelnuts will likely lead to improvements in insulin resistance as well as fat and weight loss,” compared to a diet high in saturated fats, according to a literature review published 2017 in the journal of the Missouri State Medical Association. Consequently, eating these foods with metformin may promote weight loss and help heart health because they help lower blood glucose levels.

Eat your veggies

Leafy greens, such as chard, spinach, and kale, and non-starchy vegetables, like beans, asparagus, broccoli, and tomatoes, are all rich in fiber. Fiber helps control your blood glucose levels by slowing sugar and carbohydrate absorption, which slows digestion and releases insulin more steadily. This works with metformin to enhance results.

Does metformin help with other conditions? 

Metformin’s not just used to help treat obesity; it’s also proven to ease other diseases. For example, metformin may be as effective as oral contraceptives at relieving acne and irregular menstrual cycles caused by polycystic ovary syndrome (PCOS), according to a 2020 review of studies.

And the diabetes drug was also shown to help prevent metabolic syndrome in those receiving corticosteroid treatments. 

A common side effect of corticosteroids is increased blood sugar levels. Metformin supported lower blood sugar levels and helped patients in the study avoid increases in blood sugar and insulin levels while on the corticosteroids.

In addition, metformin has been shown to reduce the risk of certain cancers, notes Rekha Kumar, MD, Found’s chief medical officer, a board-certified specialist in endocrinology, diabetes, and metabolism, adding it also has anti-aging effects for some people on a cellular level. 

What else interacts with metformin?

Taking metformin involves risk factors and potential side effects like any other medication. It's important to note that some foods may weaken a medication's efficacy or increase its side effects, which can wreak havoc on your body. Here’s a list of what can interact negatively with metformin:

Alcohol

Drinking alcohol, in general, can decrease the amount of glucose your liver releases, often resulting in low blood sugar. Because metformin already lowers blood sugar levels, it can exacerbate its effect and lead to hypoglycemia—or low blood sugar—when combined with alcohol. Your body’s response to low blood sugar can include fainting, dizziness, and lightheadedness. 

You should steer clear of alcohol entirely or substantially limit your alcohol intake. Your Found health care professional will take an individualized approach to your weight care journey and help you determine if alcohol is okay to drink while taking metformin. 

Carbonic anhydrase inhibitors

Oof—that’s a mouthful! So we’re just going to refer to these medications as CAIs, which are prescribed for glaucoma, altitude sickness, epilepsy, and other conditions. Unfortunately, they can interact with metformin and raise the risk of lactic acidosis—when the lactic acid your body naturally makes builds up to life-threatening levels. It’s crucial to let your Found physician know if you’re taking any CAI medications to avoid a dangerous reaction.

Medications that stop the body from naturally digesting and getting rid of metformin

Similar to CAIs, other drugs can cause lactic acidosis when taken with metformin. Some examples include:

• Ranolazine (Ranexa)
• Vandetanib (Caprelsa)
• Dolutegravir (Tivicay)
• Cimetidine (Tagamet HB)

Speak with your Found health care provider to get a complete list and share any medications and supplements you’re taking with your provider.

Medications that may increase blood sugar levels

Since metformin lowers blood sugar levels, medications that raise blood sugar, like some supplements with caffeine, corticosteroids, and some antipsychotics, may counteract metformin and cause high blood sugar levels. Medications that cause high blood sugar affect your body’s glucose levels. When taken with metformin, the combo may leave your body at a standstill, leading to increased blood sugar levels, and high blood sugar can cause stroke, decreased kidney function, kidney disease, and nerve pain.

It’s important to note that metformin can be helpful to counteract some of the negative metabolic effects of medicines that may raise blood sugar. Although the sugar effect is the opposite, metformin can control high blood sugar caused by some medications and doesn’t block the therapeutic effects. Ask your Found healthcare provider if your medication can help or hinder metformin.

What else to be aware of when taking metformin:

Some experience a vitamin B12 deficiency when taking a metformin dosage for weight loss and may need to take supplements to bring levels back to normal. The American Diabetes Association recommends monitoring your B12 levels if you take metformin long-term. 

Don’t worry—your Found health care provider will let you know what to do to monitor your health and if you need to take the next steps. Your care is of the utmost importance when working with your provider. Taking metformin may help with weight care, and being prescribed the medication may ensure your weight care journey is sustainable.

Found offers a science-backed weight care approach based on your unique biology, psychology, lifestyle, and prescription medication needs. The average Found member loses 10% of their body weight during their first 12 months on the program. In total, members have lost 750,000 pounds to date. To start your journey with Found, take our quiz.

SOURCES

American Diabetes Association. (2022). Non-starchy Vegetables.

https://diabetes.org/healthy-living/recipes-nutrition/eating-well/non-starchy-vegetables

American Diabetes Association; 8. Pharmacologic Approaches to Glycemic Treatment. Diabetes Care 1 January 2017; 40 (Supplement_1): S64–S74.

https://diabetesjournals.org/care/article/40/Supplement_1/S64/36805/8-Pharmacologic-Approaches-to-Glycemic-Treatment

Cahill LE, Pan A, Chiuve SE, Sun Q, Willett WC, Hu FB, Rimm EB. Fried-food consumption and risk of type 2 diabetes and coronary artery disease: a prospective study in 2 cohorts of US women and men. Am J Clin Nutr. 2014 Aug;100(2):667-75. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4095664/#bib37

Chudnovskiy R, Thompson A, Tharp K, Hellerstein M, Napoli JL, et al. (2014) Consumption of Clarified Grapefruit Juice Ameliorates High-Fat Diet Induced Insulin Resistance and Weight Gain in Mice. PLOS ONE 9(10): e108408.

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0108408

DiNicolantonio JJ, O'Keefe JH. Good Fats versus Bad Fats: A Comparison of Fatty Acids in the Promotion of Insulin Resistance, Inflammation, and Obesity. Mo Med. 2017 Jul-Aug;114(4): 303-307. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6140086/

Fraison E, Kostova E, Moran LJ, Bilal S, Ee CC, Venetis C, Costello MF. metformin versus the combined oral contraceptive pill for hirsutism, acne, and menstrual pattern in polycystic ovary syndrome. Cochrane Database Syst Rev. 2020 Aug 13;8(8):CD005552.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7437400/

GoodRX Health. 6 metformin Interactions You Should Know About. 2022 August 23.

https://www.goodrx.com/metformin/interactions

Holesh JE, Aslam S, Martin A. Physiology, Carbohydrates. [Updated 2021 Jul 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-.

https://www.ncbi.nlm.nih.gov/books/NBK459280/

Lv Z, Guo Y. metformin and Its Benefits for Various Diseases. Front Endocrinol (Lausanne). 2020 Apr 16;11:191.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7212476/

Owira PM, Ojewole JA. Grapefruit juice improves glycemic control but exacerbates metformin-induced lactic acidosis in non-diabetic rats. Methods Find Exp Clin Pharmacol. 2009 Nov;31(9):563-70.

https://pubmed.ncbi.nlm.nih.gov/20094639/

Pakkir Maideen NM, Jumale A, Balasubramaniam R. Drug Interactions of metformin Involving Drug Transporter Proteins. Adv Pharm Bull. 2017 Dec;7(4): 501-505.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5788205/

Seelig, E., Meyer, S., Timper, K., Nigro, N., Bally, M., Pernicova, I., Schuetz, P., Müller, B., Korbonits, M., & Christ-Crain, M. (2017). metformin prevents metabolic side effects during systemic glucocorticoid treatment, European Journal of Endocrinology, 176(3), 349-358.

https://eje.bioscientifica.com/view/journals/eje/176/3/349.xml

The Center for Disease Control. (2022). Fiber: The Carb That Helps You Manage Diabetes.

https://www.cdc.gov/diabetes/library/features/role-of-fiber.html

The U.S. Food and Drug Administration. (2022). Sodium in Your Diet.

https://www.fda.gov/food/nutrition-education-resources-materials/sodium-your-diet

Vinke PC, El Aidy S, van Dijk G. The Role of Supplemental Complex Dietary Carbohydrates and Gut Microbiota in Promoting Cardiometabolic and Immunological Health in Obesity: Lessons from Healthy Non-Obese Individuals. Front Nutr. 2017 Jul 24;4:34. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5523113/