Some research suggests that vitamin C supplements may benefit people with type 2 diabetes, but more studies are needed to understand the effects and recommended dosage.

Vitamin C (L-ascorbic acid) is a nutrient available in many fruits and vegetables. It’s also an antioxidant, which can help support your immune system and possibly decrease the effects of oxidative stress related to cancers, heart disease, and other chronic conditions.

Vitamin C deficiency is considered rare in the United States and other developed countries. However, having certain conditions may increase your risk of vitamin C deficiency. This includes type 2 diabetes.

If you have type 2 diabetes, you may be wondering whether you can take vitamin C supplements to help prevent deficiency and support your overall health. It’s important to talk with a doctor before taking any type of supplements, though.

This article reviews the potential benefits and risks associated with taking vitamin C supplements when you have type 2 diabetes, as well as other important information you need to know.

While vitamin C supplements are not broadly recommended for type 2 diabetes, recent research suggests there could be benefits.

According to one 2023 research review, people with type 2 diabetes were more likely to have certain nutrient deficiencies, including vitamin C. Researchers believe there may be a link between oxidative stress and glucose problems, which may decrease vitamin C levels.

The authors of the same review also suggested that people with type 2 diabetes may benefit from taking vitamin C supplements to prevent deficiency. They indicated possible other benefits, such as improved blood glucose, mood, and blood pressure.

A separate 2023 systematic review and meta-analysis of 1,447 people with type 2 diabetes found that vitamin C supplementation decreased A1C levels and improved fasting glucose and insulin. However, the authors noted that more research is needed to support these findings.

While citing similar findings, one 2021 meta-analysis in a diabetes flagship journal did not support vitamin C supplements for all people with type 2 diabetes. The authors felt that longer-term studies were needed to confirm the benefits of vitamin C for people with type 2 diabetes.

Despite the possible benefits of vitamin C supplementation for type 2 diabetes, there is no clear consensus on a recommended dosage for such purposes.

The previously mentioned 2023 review and meta-analysis found that high-dose supplements of 1,000 mg per day helped improve glycemic control when taken for longer than 12 weeks.

In general, the recommended daily allowance (RDA) for vitamin C is 75 mg per day for females 19 years and older and 90 mg for males 19 years and older. Pregnant people need 85 mg, and nursing people need 120 mg.

Ideally, it’s best to get vitamin C from the foods you eat. The vitamin is widely available in multiple plant-based food sources, such as:

  • red and green bell peppers
  • citrus fruits and juices
  • kiwifruit
  • strawberries
  • broccoli
  • tomatoes
  • green peas
  • potatoes
  • spinach

However, if a doctor determines you have a vitamin C deficiency or if you don’t eat enough vitamin C-containing foods, a supplement may be recommended.

Most multivitamins contain vitamin C, but there are also individual supplements with this nutrient only. These may be available in tablet, powder, or liquid form, with the best choice depending on your preference.

When looking at supplement labels, you may also notice there are different forms of vitamin C. As a rule of thumb, the Office of Dietary Supplements from the National Institutes of Health recommends choosing those with “simple ascorbic acid” due to its efficacy and affordability.

Unless you truly have a vitamin C deficiency, taking supplements while also eating vitamin C-rich foods could increase your risk of toxicity. Vitamin C toxicity itself is rare, but possible symptoms may include:

  • abdominal pain
  • cramps
  • nausea
  • diarrhea

It’s also important to note that vitamin C toxicity is most likely in extremely high doses. In fact, there’s a significant gap between the RDA and tolerable upper intake level (UL) for vitamin C. The UL is 2,000 mg per day for both males and females over the age of 19.

You also may want to avoid buying vitamin C supplements unnecessarily. While some brands are more affordable than others, you may not want to spend money on supplements you don’t really need.

Supplements for type 2 diabetes may be most helpful if you have nutrient deficiencies. The only way to know if you have nutrient deficiencies is through a blood test ordered by a doctor.

In general, some of the most common nutrient deficiencies in adults include:

Additionally, people with type 2 diabetes may have deficiencies in vitamins B9 and B12 due to certain medications, such as metformin. For this reason, a doctor may recommend individual supplements for these B vitamins or a multivitamin that contains both.

The previously mentioned 2023 research review also suggests that type 2 diabetes has been linked with deficiencies in vitamins C, A, and E, possibly due to oxidative stress from problems with glucose metabolism.

If you have any of the above deficiencies despite eating an overall healthy diet, a doctor may recommend supplements for support.

However, since supplements are not regulated by the FDA and can potentially interact with type 2 diabetes medications, the American Diabetes Association does not recommend taking vitamins unless your doctor specifically recommends them.

Also, while vitamin supplements can be more convenient, nutrients are absorbed most efficiently through the foods you eat.

Vitamin C is an important antioxidant that most people get from the foods they eat. However, if you have type 2 diabetes, it’s possible you may have a deficiency.

While more long-term studies are needed, current research suggests other benefits, such as improved glucose from vitamin C supplementation. It’s important to check with a doctor before taking any supplements, including widely available types like vitamin C.

If you’re concerned about a possible vitamin C deficiency from type 2 diabetes, consider talking with a doctor. They may recommend blood testing and possible supplementation if your levels are low.