What Is D-Mannose?

D-mannose is a type of sugar found in certain fruits and vegetables, including cranberries, cabbage, and tomatoes. It's also produced in the body from glucose, another form of sugar. D-mannose is also called mannose.

As a dietary supplement, D-mannose is sometimes used to prevent urinary tract infections (UTIs) or bladder inflammation (cystitis) from infections. Though more research is needed, some studies suggest it could be helpful when used alongside standard treatment.

This article describes the purported uses of D-mannose, possible side effects, and what to look for in a supplement.

Dietary supplements are not regulated like drugs in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. Choose a supplement tested by a trusted third party, such as USP, ConsumerLabs, or NSF, when possible. 

However, even if supplements are third-party tested, that doesn’t mean they are safe for all or effective in general. Therefore, it is important to talk to your healthcare provider about any supplements you plan to take and check in about potential interactions with other supplements or medications.

Supplement Facts

  • Active ingredient(s): D-Mannose
  • Alternate name(s): Mannose
  • Legal status: Recognized as a dietary supplement by the FDA, not intended to prevent or treat UTI
  • Suggested dose: D-mannose dosages ranging from 420 milligrams (mg) daily to 3 grams (g) have been used in studies. Follow the instructions on the supplement label and consult your healthcare provider.
  • Safety considerations: It can cause mild side effects; people with certain health conditions should use caution; not enough is known about its safety to support use during pregnancy, breastfeeding, or in children.

Purported Uses of D-Mannose

There is some evidence that D-mannose may prevent or treat UTIs. A number of small studies have suggested that D-mannose may help keep E. coli —the bacteria responsible for the vast majority of these infections—from sticking to the cells lining the urinary tract. More research is needed to confirm these effects. It should not be used to replace traditional treatment.

More than 7 million healthcare provider visits a year are due to this type of infection. Frequent UTIs are usually treated with a low-dose antibiotic taken for six months or longer.

Natural sources of D-mannose
 Verywell / Jessica Olah

UTI Prevention

Several studies have looked at the use of D-mannose to prevent returning UTIs:

  • A study published in the World Journal of Urology examined the use of D-mannose compared with the antibiotic nitrofurantoin or no treatment for six months in 308 women with a history of recurrent UTIs. After one week of initial treatment, both people in the supplement group and the antibiotic group had a significantly lower risk of recurrent UTIs than the no-treatment group. Still, it did not prevent recurrent UTIs in all women in the study. The people in this study used a powder formulation of D-mannose.
  • One systematic review of seven studies could not determine if taking D-mannose long-term compared with no treatment, other supplements, or antibiotics reduced the number of repeated UTIs.
  • Another systematic review of eight studies showed that D-mannose appears to have a protective effect against recurrent UTIs compared with placebo. The review also suggested that D-mannose may be similarly effective to antibiotics for prevention. However, the researchers cautioned that not enough studies are available to confirm this, and existing studies are small in size and vary in study design and quality.

When used as a supplement, D-mannose may help prevent recurrent UTIs. However, more extensive, high-quality studies are needed.

UTI Treatment

It's important to remember that supplements should not replace traditional medical treatment. If you think you have a UTI, seek medical advice from a healthcare provider.

Studies have looked at whether D-mannose can help treat active UTIs. While some research has suggested the supplement may help when used in addition to antibiotics, remember that these studies are often small and low in quality.

The following studies examined the use of D-mannose for treating UTIs:

  • A small study of 43 women found that D-mannose taken twice daily for three days during an infection followed by once a day for 10 days resulted in a significant improvement in symptoms, UTI resolution, and quality of life. Those who received D-mannose for six months following treatment had a lower recurrence rate than those who took nothing.
  • A systematic review of seven studies suggested that D-mannose may help improve UTI symptoms in the short term. However, the researchers noted that the findings were based on a limited number of small studies and should be considered cautiously.
  • A review published in 2015 concluded that there is a lack of strong evidence that D-mannose—and other remedies like cranberry juice and vitamin C—should be used as a replacement for antibiotics in treating UTIs.

Research is ongoing and more studies are needed.

D-mannose powder

MonaMakela / Getty Images

What Are the Side Effects of D-Mannose?

Common side effects of D-mannose reported in studies include:


Since D-mannose exits the body in urine, there is some concern that high doses may injure or impair the kidneys.

D-mannose can also potentially affect blood glucose levels in people with diabetes.

Not enough is known about the safety of the supplement during pregnancy or breastfeeding, so it should be avoided. Children shouldn't take D-mannose, either.

You should not self-treat a UTI with D-mannose or otherwise avoid or delay standard care, as doing so can lead to serious complications, including a kidney infection and even permanent kidney damage.

Dosage: How Much D-mannose Should I Take?

While D-mannose is typically considered safe because it occurs naturally in many foods, doses higher than consumed through a normal diet may be toxic or otherwise harmful. In addition, little is known about the long-term safety of D-mannose at any dose.

There are currently no standard guidelines for D-mannose dosages. In studies, D-mannose dosages have ranged from as little as 420 milligrams per day to 3 grams in various supplement forms.

Consult your healthcare provider before taking D-mannose to confirm how much you should take.

Frequently Asked Questions

  • Will taking D-mannose prevent or treat UTIs?

    Some research has suggested that D-mannose supplementation helps prevent recurrent UTIs when compared with a placebo. It may also be similarly effective to antibiotics for preventive use. However, larger, higher-quality studies are needed to confirm these findings.

    There is less evidence to suggest that D-mannose will treat an active UTI. However, studies have shown that, when used in addition to antibiotics, it may help improve symptoms. Therefore, never use D-mannose as a replacement for standard treatment.

    Although it may help, D-mannose isn't guaranteed to prevent UTIs from returning. If you experience recurrent UTIs, make an appointment with your healthcare provider to determine your best plan of action. Always consult a healthcare provider before starting any new supplement.

  • What sources of D-mannose are available?

    D-mannose can be consumed through food such as cranberries, green beans, and tomatoes. It is also available in oral supplement form as capsules or a powder mixed in with water or unsweetened juice.

  • What are the side effects of taking D-mannose?

    D-mannose is considered relatively safe and well-tolerated. Side effects such as diarrhea and bloating can happen. It can also potentially harm the kidneys if taken in high doses.

    Talk to your healthcare provider before starting D-mannose to ensure it is safe for you, especially if you have any health conditions.

Sources of D-mannose & What to Look For

D-mannose occurs naturally in:

  • Cranberries
  • Black and red currants
  • Peaches
  • Green beans
  • Cabbage
  • Tomatoes

D-mannose supplements are available in capsule or powder form. D-mannose powder is mixed with water or unsweetened juice and taken as a liquid.

It's important to remember that dietary supplements haven't been tested for safety and are largely unregulated in the United States.

When shopping for supplements, look for products certified by ConsumerLab, The U.S. Pharmacopeial Convention, or NSF International. These organizations don't guarantee a product is safe or effective, but their seal indicates that a supplement has undergone testing for quality.


Preliminary studies suggest that D-mannose holds promise as a way to help prevent UTIs. However, larger, high-quality studies are needed to confirm the findings and the safety of D-mannose supplements.

If you're still thinking of trying D-mannose to prevent UTIs, talk with your healthcare provider first to weigh the pros and cons and decide whether it's a good option for you.

12 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Jennifer Lefton, MS, RD/N, CNSC, FAND
Jennifer Lefton, MS, RD/N-AP, CNSC, FAND is a Registered Dietitian/Nutritionist and writer with over 20 years of experience in clinical nutrition. Her experience ranges from counseling cardiac rehabilitation clients to managing the nutrition needs of complex surgical patients.

Originally written by Cathy Wong
Cathy Wong

Cathy Wong is a nutritionist and wellness expert. Her work is regularly featured in media such as First For Women, Woman's World, and Natural Health.

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