D-Mannose for UTI: What is it and Does it Work?

By Irmanie Hemphill, MD, FAAFP
Medically reviewed
March 1, 2021

When you think you have a urinary tract infection (UTI), you want it gone—now! It’s tempting to try everything that you read online might help alleviate the burning and urgency. Unfortunately, many of these “cures” are not proven by science to actually make a UTI go away. And if you delay seeking treatment from a healthcare provider, you may make things worse.

That’s why we want to talk about D-mannose. This supplement is one of the common remedies you may read about online. But does it truly help—and what are the potential side effects if you take it? We want you to feel better as soon as possible and to fully eliminate the bacteria causing your UTI, so we took a look at the research on D-mannose. 

UTI Symptoms and Causes

UTIs are rarely subtle. When you have one, you typically suspect it. The most common UTI symptoms are:

  • An intense, persistent, and frequent urge to urinate
  • A burning sensation or pain during urination
  • Passing frequent, small amounts of urine
  • Cloud-colored urine
  • Blood in the urine
  • Strong or foul-smelling urine
  • Pelvic pain
  • Pain in the side, lower abdomen, or back
  • Nausea and/or vomiting
  • Fever

What’s causing all of this? UTIs happen when bacteria enters the urethra and multiplies in one or more parts of the urinary tract. About 80 to 90 percent of UTIs are caused by escherichia coli (a.k.a. e. coli bacteria). However, UTIs can also be caused by other bacteria or fungi. 

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What Is D-Mannose?

You may have heard about D-mannose for treating UTIs. D-mannose is a carbohydrate. It’s a simple sugar that is structurally similar to glucose. D-mannose is found in foods such as:

  • cranberries (and cranberry juice)
  • oranges 
  • apples 
  • peaches
  • mangoes
  • legumes

You can also find D-mannose in dietary supplements. Some supplements add other ingredients such as cranberry powder. Now, let’s look at what scientific evidence there is for using these pills.

Does D-Mannose Help Treat UTIs?

When someone consumes sufficient amounts of D-mannose, such as the doses found in dietary supplements, it’s absorbed in the urinary tract. There it attaches to e. coli so that the bacteria can’t take up residence in urethra, bladder, or ureters. 

And if e. coli can’t get cozy in the urinary tract or stick to the bladder wall, it can’t grow and cause infection. Instead, eventually our body eliminates the D-mannose and e. coli when we urinate. 

Considering how it works, it seems like taking D-mannose would be a great way to prevent UTIs or treat them. But before you buy supplements, let’s look at what the scientific studies on D-mannose as a prophylactic to prevent UTI have found.

2014 Study

In a 2014 study, researchers examined women with recurrent urinary tract infections. “Recurrent” UTIs are defined by having three or more UTIs in a year or or two or more UTIs in six months.

Everyone participant took an antibiotic first. 

Then, for six months:

  • One third of the women took 2 grams of D-mannose powder daily
  • One third took a daily antibiotic (nitrofurantoin)
  • The last third received no treatment

The D-mannose group experienced the same reduction in risk of UTI as the antibiotic treatment group did.

2016 Study

In a 2016 pilot study of 43 adult women with UTI or symptoms of a bladder infection. These women took oral D-mannose twice daily for three days and then once a day for 10 days.

After this, they checked their symptoms and tested for bacteria in the urine (called bacteriuria). Most reported improved symptoms and only one woman who took D-mannose had another UTI during that time.

The Most Recent Research (2020 Study)

Two systematic reviews published in 2020 each examined clinical trials on the use of D-mannose to help prevent recurrent urinary tract infections.

  • The first meta-analysis concluded that D-mannose appears to be about as effective as antibiotics at reducing recurrent UTI and also has minimal side effects. 
  • The second review also concluded that the supplement seems to decrease the likelihood of recurrent UTI and improve quality of life by reducing symptoms.

This is all promising support, but in the medical community, eight studies is not enough to make a definitive judgment on whether D-mannose can prevent UTI. More research is necessary to confirm the effectiveness of D-mannose.

How to Take D-Mannose for Urinary Tract Infections

As of right now, there is no standard dosage for D-mannose for UTIs. To add to the confusion, each study has used slightly different dosages. As a few examples:

  • 2 grams daily for six months
  • 1.5 grams twice daily for three days, then once daily for 10 days
  • 1.5 grams twice daily for 16 weeks
  • 1 gram three times a day for two weeks, then twice daily for 22 weeks
  • 1 gram three times a day for five days
  • 500 milligrams (half a gram) twice a day for seven days

Talk to your doctor to determine how much D-mannose to take, how often, and for how many days.

When you look at supplements, try to find ones that are third-party verified. This means they’ve been independently tested to confirm that the dietary supplement contains what the label says it contains, at the amount the label states, and that nothing else other than the ingredients listed are in the supplement. This is important because the FDA does not regulate dietary supplements. 

You can find D-mannose in capsules or as a powder. If you use the powder, mix it with water as directed on the package. Be sure to check how much D-mannose each capsule or scoop of powder provides so that you take the correct amount.

Are There Side Effects of D-Mannose?

Side effects when taking oral D-mannose appear to be rare. The most common ones reported are diarrhea or loose stools. But only a small percentage of people seem to experience this side effect.

Note that if you have diabetes, it’s even more important to talk to your doctor before taking D-mannose. The thinking is that, since D-mannose is a type of sugar, it may impact blood sugar levels. Give your doctor a heads up so that you can both monitor your blood sugar levels if you decide to take D-mannose.

What is the Best Way to Treat a UTI?

With limited yet promising support, D-mannose is not the best way to treat a UTI. Neither is cranberry juice or probiotics. What is? Antibiotics such as trimethoprim or nitrofurantoin

But you need to take the right antibiotic to fight the specific bacteria in your urinary tract. This might be e. coli, or it could be another microorganism. 

So see your doctor if you think you have a UTI. They can perform a urine culture to identify the bacteria causing your infection. Once they identify that, they can determine which antibiotic would be best to take.

It also doesn’t hurt to stay hydrated. Drinking plenty of water will make you want to go to the bathroom more frequently, and this may help flush out the pathogens. 

When to See a Doctor

If you delay treating a urinary tract infection, you risk having the infection spread. If that happens, it can lead to a kidney infection or even long-term kidney damage or sepsis, a sometimes life-threatening reaction to infection. 

The lesson: Call your doctor if you have even the slightest notion that you have a UTI. Most are easily treated with antibiotics, and an accurate diagnosis will also rule out other possible health issues, such as a sexually transmitted disease. Whatever your health care provider finds, they can then recommend the best plan of action to treat that problem. As they say, better safe than sorry.

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How K Health Can Help

Did you know you can get affordable UTI treatment with the K Health app? Download K to check your symptoms using our AI-driven symptom checker and, if needed, text with a doctor in minutes. K Health’s board-certified, U.S.-based doctors can provide a treatment plan and prescription to resolve your symptoms as soon as possible.

Frequently Asked Questions

Can D-mannose cure a UTI?
Scientific evidence does not indicate that D-mannose can cure a UTI. The evidence only shows that D-mannose appears to help prevent recurrent UTI.
How much D-mannose do you take for a UTI?
There is no standard dosage for D-mannose for UTIs. Studies on oral D-mannose to help prevent UTI have used amounts as varied as 420 milligrams to 2 grams a day, and some studies suggest taking D-mannose more than once a day. If you wish to try D-mannose for a UTI, ask your doctor how much you should take, how often, and for how many days.
Can D-mannose cause kidney damage?
There is no scientific evidence to suggest that D-mannose can cause kidney damage.
How long does D-mannose take to work?
Our bodies rapidly absorb D-mannose; it reaches the organs in about half an hour.
K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Irmanie Hemphill, MD, FAAFP

Dr. Hemphill is an award winning primary care physician with an MD from Florida State University College of Medicine. She completed her residency at Halifax Medical Center.