Overview

Cranberry juice and cranberry dietary supplements are commonly used to prevent kidney or bladder infections in certain people. Certain chemicals in cranberries seem to prevent bacteria from clinging to the bladder wall, which may help prevent an infection. Common side effects may include diarrhea or an upset stomach. Before taking cranberry, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is cranberry used for?

Cranberry (Vaccinium macrocarpon) is commonly used by certain people to prevent kidney or bladder infections (urinary tract infections, or UTIs).

Note: The FDA has not reviewed cranberry for safety and effectiveness. Learn more about dietary supplements here.

How does cranberry work (mechanism of action)?

Cranberry is the berry of a plant called Vaccinium macrocarpon. It is commonly consumed as a food or juice. It is also available as dietary supplements.

Cranberries contain chemicals called proanthocyanidins (PACs). These chemicals can help stop bacteria from clinging to the wall of the bladder. This may help prevent a new urinary tract infection in certain people who often get these types of infections.

However, the chemicals in cranberries do not kill bacteria that are already clinging to the wall of the bladder. Cranberry juice and cranberry dietary supplements are not beneficial for treating people who already have an infection in the kidney or bladder.

Herbal products, such as cranberries, naturally contain many different chemicals, including PACs. But the amounts of each chemical in a specific cranberry juice or dietary supplement may vary widely from product to product. Studies show that cranberry juice and cranberry dietary supplements must contain a certain amount of pure cranberry to help prevent urinary tract infections. Juices should contain at least 27% cranberry and be taken as a full glass daily. Dietary supplements should provide at least 500 mg pure cranberry per day.

How should I store cranberry?

You should store cranberry supplements according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of cranberries?

The most common side effects of cranberries are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Diarrhea
• Upset stomach

There may be other side effects of cranberries that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of cranberry?

While less common, the most serious side effects of cranberry are described below, along with what to do if they happen.

Severe Allergic Reactions. Cranberry may cause allergic reactions, which can be serious. Stop taking cranberry and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives, which can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Precautions

Who should not use cranberry?

Allergies to Ingredients. People who are allergic to any of the following should not take cranberry.

• Cranberry
• Vaccinium macrocarpon
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific cranberry products they stock.

What should I know about cranberry before using it?

Cranberry is available as a food, juice, and dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep cranberry out of the reach of children.

If you have symptoms of an infection in the kidney or bladder (also known as a urinary tract infection, or UTI), call your health care provider. Cranberries do not seem to help treat an existing urinary tract infection.

Herbal products, such as cranberries, naturally contain many different chemicals. The amount of each chemical in a specific cranberry product can vary for many reasons. If you switch to a new bottle or a different brand, you may not have the same effects or side effects because of this variability. Talk to your health care provider if you have questions or concerns.

Some juices and dietary supplements do not contain pure cranberry. For example, cranberry juice products may only contain a small amount of cranberry mixed with water. If you are using cranberry to prevent a kidney or bladder infection, make sure that the product you are using contains enough cranberry. Studies show that juices should contain at least 27% cranberry, and that you should drink at least 8 ounces each day. Dietary supplements should provide at least 500 mg of pure cranberry per day.

The FDA has not tested cranberry products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using cranberry?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if cranberry is right for you.

In particular, make sure that you discuss any of the following.

Kidney Stones.Cranberry might increase your risk of certain types of kidney stones. If you have had kidney stones in the past, talk to your health care provider before taking cranberry.

Other Medicines and Supplements.Cranberry may interact with other medicines and supplements. Before taking cranberry, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how cranberry could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if cranberry passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does cranberry interact with foods or drinks?

There are no known interactions between cranberry and foods or drinks.

It is unknown if drinking alcohol will affect cranberry.

Does cranberry interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using warfarin, which is a blood thinner.

Cranberry dietary supplements may also alter the blood levels of some medicines. Tell your health care provider about all medicines that you take or have recently taken.

The interactions between cranberry and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with cranberry is incomplete. Always check with your health care provider before using cranberry with any medicines.

Dosing

What should I do if I accidentally use too much cranberry?

If you or someone else has used too much cranberry, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Read the product label closely and speak with a health care provider about how to use cranberry safely. If you miss a dose, take it as soon as you remember. Do not take double or extra doses.