Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started
My Medicine

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Font Size


Chitosan is a type of fiber taken from the shells of crustaceans such as:

  • Shrimp
  • Clams
  • Lobster

Why do people take chitosan?

Some people take chitosan to try to lose weight. Chitosan is sold over the counter as a "fat blocker" or "fat trapper." The claim is that the supplement might reduce the amount of fat absorbed in your gastrointestinal tract. The FDA has warned about such claims. It says there is no reliable scientific evidence. A review of high-quality studies shows that overweight people who took chitosan did not lose significant amounts of weight.

Scientists have also looked at whether chitosan helps lower cholesterol levels. In some recent well-designed studies, chitosan reduced total cholesterol as well as LDL "bad" cholesterol. But more research is needed.

Early studies in people have hinted that varying forms of chitosan might also help:

Again, more research is needed to study chitosan for these conditions.

Optimal doses of chitosan have not been set for any condition. Quality and active ingredients in supplements may vary widely. This makes it hard to set a standard dose.

Can you get chitosan naturally from foods?

No. Chitosan is not found naturally in foods. It is extracted from a substance in shells of crustaceans.

What are the risks of taking chitosan?

Chitosan supplements appear to be safe when taken for a short time.

Side effects may include:

If you are allergic to shellfish, you should not take chitosan.

Chitosan may interfere with how blood thinners work in your body. If you take warfarin, talk to your doctor before taking this supplement.

Animal studies show that chitosan may cause a slight decrease in blood sugar. Talk to your doctor first if you are taking any medicines for diabetes.

Chitosan may also prevent your body from absorbing fat-soluble vitamins such as vitamins A, D, E, and K. Magnesium may also not be absorbed.

Always tell your doctor about any supplements you are taking, including natural ones and those bought without a prescription. That way, your doctor can check on any potential side effects or interactions with any medications.

WebMD Medical Reference

Reviewed by David T. Derrer, MD on December 07, 2014

Vitamins and
Lifestyle Guide

Which Nutrients
Are You Missing?

Learn More

Today on WebMD

vitamin rich groceries
Do you know your vitamin ABCs?
St Johns wart
Ease hot flashes and other symptoms.
Are you getting enough?
Take your medication
Wonder pill or overkill?
fruits and vegetables
Woman sleeping
Woman staring into space with coffee

Send yourself a link to download the app.

Loading ...

Please wait...

This feature is temporarily unavailable. Please try again later.


Now check your email account on your mobile phone to download your new app.