April 22, 2023

Foods to Avoid While Taking Metformin

If you have been newly diagnosed with Type 2 Diabetes, it is common for doctors to start you on a drug called Metformin. As a patient, getting a Type 2 Diabetes diagnosis can be overwhelming and scary. New medicine, new diet, the pressure to make all these changes immediately and do it well. Seeking support if you feel this way is crucial! You are not alone, and there is help out there (us included). 

In this article, you’ll learn what Metformin is, foods to avoid while taking metformin, and some foods that are helpful to incorporate when you are facing a new diabetes diagnosis. 


What is metformin?

Metformin is available as a liquid, a tablet, and an extended-release tablet that are all taken by mouth.

Metformin is considered a “first-line medication” for treating Type 2 Diabetes. This means that when a person is first diagnosed with Type 2 Diabetes or even prediabetes, metformin is often one of the first treatments doctors try. Depending on the current blood sugar control and hemoglobin a1c (this is a number that represents an average of your blood glucose levels over the past few months) of a patient, doctors may try metformin only for a while, or they may combine it with other medications like insulin. 


How does metformin work?

In a nutshell, metformin helps lower our baseline (aka fasting) blood sugar levels and blood sugar levels after we eat (aka postprandial blood sugar). 

Metformin does all of this in a few ways [1]:

1. Makes our body more sensitive to insulin

It helps to restore the body’s natural response to insulin. Insulin is a hormone, and its job is to help cells in our body take in sugar from our blood to use it for energy. This means the sugar leaves our blood, and thus blood sugar levels are well-managed. 

Think of a kids’ basketball game with very obedient team members. The coach yells out “Brian, get there! Susie, go to the net!” And then the kids quickly and obediently do as they’re told and get to the net or wherever the coach directs. Think of insulin as the basketball coach for your blood sugar. It tells the sugar where to go and when to go. When we have good insulin sensitivity, that sugar hustles and gets into your cells, instead of hanging around in the bloodstream. Metformin makes our bodies respond to the commands of insulin, resulting in better blood sugar control.

2. Reduces the amount of sugar that the liver produces

Did you know the liver can produce sugar?! Unless you took a LOT of organic chemistry courses, you probably didn’t know this. The liver is a workhorse. One of its jobs is to act like a fuel reservoir. It can store glucose (aka sugar) for us, and create it to be released into the blood when needed. 

These are all normal processes (some science terms: glycogenolysis and gluconeogenesis). However, when we are dealing with insulin resistance, more sugar to the mix from the liver is not helpful. This is why it is good that Metformin tampers down this pathway a bit, contributing to improved blood sugar control. 

3. Reduces the amount of blood sugar that the intestines absorb during digestion

After we eat, carbohydrates are broken down to sugar, and that sugar gets absorbed from your intestines into your bloodstream. Metformin causes less sugar from our foods to be absorbed, which means a lower blood sugar spike after eating.


Now that we established some baseline knowledge, let’s address what many of you likely came to this article for. Are there foods to avoid while taking metformin? Per MedlinePlus, an online health information resource from the National Library of Medicine (NLM), which is part of the National Institutes of Health (NIH), the only dietary guideline for taking metformin is to “be sure to follow all exercise and dietary recommendations made by your doctor or dietitian. It is important to eat a healthful diet” [2].

Okay, decent advice. For some patients, this feels like enough information. If you’re in the camp of wanting to know more details, read on for our take on foods to avoid while taking metformin as well as foods to incorporate to help with blood sugar management aka general healthful advice from your virtual neighborhood dietitian.


Foods or drinks to consider reducing or avoiding while taking metformin

Alcohol and high amounts of simple or refined carbohydrates are the most direct answers to the question of what foods to avoid or reduce while taking metformin. 

  • Alcohol

Also good advice for general health, but take extra care to avoid excessive drinking (if you drink at all) while taking metformin. The CDC defines drinking in moderation as no more than 1 drink per day for women, and no more than 2 drinks per day for men [3]. 

Excess alcohol can negatively interact with metformin and lead to very low blood sugar levels or hypoglycemia. Hypoglycemia can be very dangerous, so this is not something to mess around with. This is a great topic to discuss with your primary care provider if you do drink and are starting metformin.


  • High amounts of simple or refined carbohydrates

While all humans need carbohydrates, we want to focus on nutrient-dense carbohydrates as outlined below. High amounts of refined carbohydrates (think white breads, pastries, sugar-sweetened beverages, sweets) will lead to higher blood sugar levels. Simple or refined carbohydrates differ from complex or nutrient-dense carbohydrates in that they have lower amounts of nutrients like fiber, vitamins and minerals. 

When you are taking metformin and consuming high levels of refined carbohydrates, this is like trying to paddle upstream. Lots of simple sugars make metformin and your body have to work that much harder, and ultimately it’s a losing battle. When taking metformin, it is important to choose foods that are supportive of blood sugar management. 


If someone who has prediabetes or diabetes and is taking metformin also has heart health concerns, like high blood pressure, high cholesterol, a heart attack, or has been diagnosed with coronary artery disease, it is also advised to reduce saturated and trans fat intake as well as sodium.

  • High amounts of saturated or trans fats

Often, prediabetes or diabetes may co-occur with conditions like hypertension (aka high blood pressure) or cardiovascular disease. To support your health in these cases, it is best to avoid overdoing it on foods high in saturated or trans fats. This includes red meat, processed meats and fried foods. Instead, it is best to focus on increasing variety in your diet and including other protein sources that are lower in these types of fats and higher in monounsaturated and polyunsaturated fats (these are what you may hear referred to as the “good types of fats”) – such as fish, seafood, nuts, and seeds.

  • Sodium

If you have high blood pressure or a family history of high blood pressure, your doctor or dietitian may advise you to reduce sodium in your diet. This is because high amounts of sodium can cause our body to retain more water, and that water in part is in our bloodstream. When we have more volume going through the same size vessels, this puts pressure on the vessel walls, thus increasing blood pressure. The average American consumes about 3,400mg of sodium per day, while current Dietary Guidelines for Americans recommend no more than 2,300mg for most adults [4]. 


Foods to incorporate while taking metformin aka general healthful advice

There are so many wonderful foods you can incorporate to support blood sugar management, which can go hand in hand with eating for prevention or treatment of other conditions like metabolic syndrome as well as general heart health.

  • Nutrient-dense carbohydrates

Nutrient-dense carbohydrates include whole grains, legumes (like beans, peas, lentils), starchy vegetables (like potatoes and corn) and fruits. Nutrient-dense carbohydrates give us more bang for our nutritional buck in the form of more fiber, more protein, and more micronutrients our bodies need.

Humans, regardless of whether they have prediabetes or diabetes, need carbohydrates. That is why we included the list above. Carbohydrates are the preferred source of energy for our bodies. When we include nutrient-dense forms of carbohydrates in appropriate amounts for our bodies, that is when the body is best able to manage blood sugar and energy levels.

  • Non-Starchy Vegetables

In addition to starchy vegetables, non-starchy vegetables play a huge role in blood sugar management. The list here is endless – artichokes,