Aug 09, 2023

5 Supplements You Shouldn't Be Taking if You Have Diabetes, According to a Dietitian

In addition to diet and exercise, can supplements help with diabetes? Learn more about 5 supplements you might want to reconsider taking if you have diabetes.

Barbie Cervoni, MS, RD, CD/N, CDE, is a Registered Dietitian (RD) and Certified Diabetes Care and Education Specialist (CDCES). She strongly believes that both nutrition and diabetes education is the impetus for achieving one of her primary objectives—that is, guiding her patients to achieving the healthiest version of themselves. She is a freelance writer and medical review board memeber for Verywell. She is also the owner and founder of

Jessica Ball, M.S., RD, has been with EatingWell for three years and works as the associate nutrition editor for the brand. She is a registered dietitian with a master's in food, nutrition and sustainability. In addition to EatingWell, her work has appeared in Food & Wine, Real Simple, Parents, Better Homes and Gardens and MyRecipes.

When it comes to managing diabetes, lifestyle plays a major role in blood sugar management and overall health. What you eat, how you move your body, your sleeping patterns and stress levels are all factors that can impact your blood sugars. Even if you are taking medications to manage your diabetes, they are to be used in conjunction with a nutritious eating plan and physical activity. But, what about supplements? Are they safe and effective?

Supplements are meant to fill nutrient gaps when you are unable to meet your needs through food alone or if you have a deficiency. Because supplements are not regulated by the Food and Drug Administration, it's important to take them cautiously. Always look for third-party certification to assure what they say is in it actually is and never begin supplementation without supervision from a registered dietitian or medical doctor. Supplements can be costly and if not taken carefully may do harm, especially if you are taking certain medications or have other health conditions.

There are different types of diabetes and different treatment options for each type, so it's difficult to generalize which supplements all people with diabetes should not take. That's one of the reasons it is so important to talk to a health professional. All that said, here are five supplements you may want to reconsider if you have diabetes, as they may interfere with certain medications, disrupt blood sugar levels or cause unwanted side effects.

Chromium is a mineral that is found in a number of foods, such as meat, vegetables, grains, fruits and nuts. A deficiency in chromium may cause high blood sugar; however, deficiency is very rare. If you have diabetes and take insulin or other oral medications aimed to reduce blood sugar, taking chromium may increase the risk of hypoglycemia (low blood sugar).

The American Diabetes Association cautions anyone with kidney disease against taking chromium because supplementation can worsen kidney disease. Chromium supplementation may also interfere with levothyroxine (a medication commonly used to treat hypothyroidism).

Bitter melon is an herbal supplement that has been studied for its use in reducing blood sugars in people with diabetes. Its components—charantin, vicine and polypeptide-p—are thought to have a similar structure to insulin (the hormone involved in blood sugar control).

In a systematic review and meta-analysis in Nature, researchers found that the data on bitter melon supplementation continues to remain inconsistent. Studies that have been done are short, and the doses of bitter melon used vary. More research is needed to determine long-term effects and safety. In addition, if you are prone to low blood sugar, bitter melon may increase your risk of low blood sugar and may not be appropriate for you.

Drinking green tea has been shown to provide benefits for people with diabetes. For example, in a meta-analysis of 17 clinical trials published in The American Journal of Clinical Nutrition, researchers found that drinking green tea had favorable effects, such as decreased fasting glucose and hemoglobin A1C (three-month average of blood sugar). However, there is little research on the effectiveness of a green tea supplement outside of studies conducted on animals, and most studies have been very short in duration. Therefore, additional supplementation beyond drinking green tea is probably not necessary.

More research is needed on the use of St. John's wort and diabetes, due its potential effects on diabetes medications, insulin sensitivity and insulin secretion. One small study in the British Journal of Clinical Pharmacology, which evaluated the use of St. John's wort and metformin in 20 healthy male subjects, found that taking it in conjunction with metformin can increase insulin secretion and lower blood sugar after a glucose tolerance test. However, another very small study, including 10 healthy male subjects, found that there were no changes in insulin sensitivity when taking St. John's wort alone. Instead, researchers noted less insulin secretion, which can increase blood sugar levels.

These very small studies had conflicting results and did not include diverse populations or people with diabetes or have a long enough duration to examine the long-term effects. Therefore, more studies are needed to explore the drug-herb interactions, as well as insulin secretion effects of St. John's wort.

In addition, if you have diabetes and heart disease and are taking blood thinners, the ADA recommends avoiding St. John's wort, as it can increase bleeding.

Vitamin E is a powerful antioxidant that can help combat oxidative stress, a precursor and contributor to type 2 diabetes. But, vitamin E can interact with blood thinners and increase the risk for bleeding by blocking the clotting effects of vitamin K. Therefore, unsupervised supplementation is not recommended if you have diabetes and are taking blood thinners.

Before spending lots of money on supplements that may not work or can cause harm, focus on making simple yet sustainable dietary changes. Whole foods contain a variety of macronutrients, vitamins and minerals. Aim to increase your intake of plants—fruits, vegetables, whole grains, nuts and seeds—that are rich in fiber, vitamins, minerals, antioxidants and healthy fats.

Fiber is the indigestible part of carbohydrate that can help to reduce blood sugar spikes because it is metabolized slowly. One simple way to eat more fiber is to ingest one fruit or vegetable at each meal, make half of your grains whole grains, and add one serving of unsalted nuts each day. The 2020-2025 Dietary Guidelines for Americans recommends consuming 25 to 38 grams of fiber daily. If you are not accustomed to eating fibrous foods, increase your intake slowly and drink ample amounts of fluids to reduce the risk of stomach discomfort, such as gas.

When eating carbohydrates (grains, potatoes, beans, corn), pair them with nonstarchy vegetables, lean protein and healthy fats. This food combination will not only provide satiating power, but also it will help you up your intake of vitamins, minerals, essential fats and protein. A simple yet effective strategy is to use the plate method. Fill half of your plate with nonstarchy vegetables, one quarter with lean protein, and the other quarter with a complex carbohydrate. For example, roasted chicken with stir-fried broccoli and baked sweet potato is a balanced and filling meal.

It is very important not to replace medical treatment with over-the-counter products that claim to treat diabetes. Treatment of diabetes is ongoing and requires daily diabetes self-management. Lifestyle changes, such as eating a nutritious diet, weight loss (when indicated), physical activity, adequate sleep and reducing stress can help you manage your diabetes. Unfortunately, there is no supplement that will cure you.

If you are deficient in a vitamin, you may benefit from supplementation. And if you have complications of diabetes, some supplements—including vitamin D, B vitamins, omega-3 fatty acids and probiotics—may help with symptoms or delay the progression of complications related to diabetes.

Vitamin D: Having low levels of vitamin D is associated with the development of diabetes, metabolic syndrome and insulin resistance. Low vitamin D levels are also associated with an increased risk of foot ulcers and other infections, feelings of depression and impaired bone health, to name a few. Some studies suggest that supplementing with vitamin D and calcium, in people who are deficient, may help to improve blood sugar control. It is important for all people with diabetes to assess their vitamin D status with their health care provider to determine if supplementation is needed.

B vitamins and omega-3 fatty acids: People with diabetes, particularly those who take metformin, can be at increased risk of vitamin B12 deficiency. Metformin can reduce the absorption of B12 as well as blood concentrations. B12 deficiency and insufficiency is associated with neuropathy, so assessing B12 status is important. If levels are low, supplementation may be recommended. If you have complications of diabetes, such as neuropathy (nerve damage), you may want to discuss with your doctor the use of B vitamins or fish oil in treating pain and preventing the progression of disease. Animal studies have shown omega-3 fatty acid supplementation to be beneficial, but more research is needed.

Probiotics: There is growing evidence to support the use of probiotics for gut health, diabetes and blood sugar control. Some studies have shown that the use of probiotics like yogurt, fermented milk and capsules had a beneficial effect on blood sugar control. Keep in mind that different strains of probiotics have different functions, and your dietary patterns, along with the amount of colony units you take, can also have an impact. If you want to take a supplement, be sure to talk to a professional. A good place to start increasing your probiotic intake is by adding some fermented foods to your diet; try yogurt, kefir, kimchi, sauerkraut and miso.

While supplements can serve a purpose when you need to fill nutrient gaps or when you are deficient, they are not always safe, and oftentimes we don't know their long-term effects. Therefore, before you spend money on supplements, take a look at your lifestyle. A foods-first approach is a safer, more affordable and more realistic way to prevent and manage diabetes. Eating a variety of fruits, vegetables, whole grains, nuts, seeds and lean protein can help you to manage blood sugars and inflammation (another key factor in diabetes).

If you have diabetes, or take care of someone who does, and don't know where to start, meet with a registered dietitian or certified diabetes care and education specialist. Before taking any supplements, discuss it with your health care provider.

Vitamin D B vitamins and omega-3 fatty acids Probiotics