AIDS-Related Diarrhea

Date: April 1, 1995
Source: National Institutes of Health (NIH)
Author: National Institute of Allergy and Infectious Diseases (NIAID)

In the United States, almost all people with AIDS develop diarrhea at some time in the course of their disease. Severe or prolonged diarrhea can lead to weight loss and malnutrition. The excessive loss of fluid that may occur with AIDS-related diarrhea can be life-threatening.


Diarrhea, which means two or more loose or unformed stools per day, can last for a few days or can be chronic, lasting for weeks or months. Many people with AIDS have diarrhea that persists for more than a month or is so severe they expel several gallons of fluid a day. The diarrhea may be accompanied by abdominal cramps, nausea, vomiting, fever, blood in the stool or weakness.


There are many possible causes of diarrhea in people who have AIDS. The most common infectious organisms causing AIDS-related diarrhea include cytomegalovirus (CMV); the parasites Cryptosporidium, microsporidia and Giardia lamblia; and the bacterium Mycobacterium avium-intracellulare (MAC). Other bacteria and parasites that cause diarrheal symptoms in otherwise healthy people may cause more severe, prolonged or recurrent diarrhea in people with HIV or AIDS.

Diarrhea also can have non-infectious causes. These include: antibiotics or other drugs that can destroy beneficial bacteria in the intestines; HIV enteropathy, which is disease caused by HIV itself; cancers such as non-Hodgkin's lymphoma or Kaposi's sarcoma; and lactose intolerance, irritable bowel or other gastrointestinal disorders. For example, most people with AIDS are lactose intolerant, which means they cannot digest lactose, a milk sugar. When they eat dairy products such as milk, cheese or ice cream they may develop diarrhea, cramping and gas. Sometimes, diarrhea can stem from a lack of stomach acids, a condition that is common in people with AIDS.


It is important to determine the cause of diarrhea so that the best treatment can be offered. Doctors examine stool samples to determine whether diarrhea-causing organisms are present. Doctors also may need to take small samples of tissue from the stomach or intestines to detect diarrhea-causing organisms or determine if cancer is present. These tests can identify the cause of diarrhea in most people with AIDS.


If doctors identify an organism as the cause of a person's diarrhea, they prescribe the antibiotics known to be effective against that organism. There is no established treatment to combat diarrhea caused by Cryptosporidium or micro-sporidia. However, in some people with AIDS, Crypto-sporidium diarrhea goes away without treatment. Whether or not a microbe can be identified as the cause of diarrhea, patients should receive symptomatic treatment such as antidiarrheal agents, and fluids and nutrients by mouth or through a vein to replace what is expelled in their diarrhea. It is helpful for patients to have counseling about their diet, emphasizing the importance of adequate fluid intake as well as small, frequent nutritious meals. Most patients with diarrhea should avoid gas-causing foods, fats and dairy products.

Maintenance and Preventive Therapy

Diarrhea caused by certain bacteria may require lifelong treatment with oral antibiotics to prevent it from coming back. This is called maintenance therapy. A U.S. Public Service task force recommended that people who have MAC should be treated with at least two drugs, one of which should be either azithromycin or clarithromycin.

In addition, the task force recommended that people infected with HIV (the virus that causes AIDS) who have fewer than 100 CD4+ T cells should be treated with rifabutin to prevent an initial episode of MAC. (CD4+ T cells are the crucial immune cells targeted by HIV.) Drug regimens to prevent the other causes of infectious diarrhea are not recommended at this time.


The National Institute of Allergy and Infectious Diseases (NIAID) funds research aimed at finding new drugs to treat people with AIDS-associated diarrhea. Several new therapies are being evaluated for safety and effectiveness in NIAID-sponsored clinical trials. For more information on these and other studies, call the AIDS Clinical Trials Information Service: 1-800-TRIALS-A 1-800-243-7012 (TDD/Deaf Access)

For federally approved treatment guidelines on HIV/AIDS, call the HIV/AIDS Treatment Information Service: 1-800-HIV-0440 1-800-243-7012 (TDD/Deaf Access)

NIAID, a component of the National Institutes of Health, supports research on AIDS, tuberculosis and other infectious diseases as well as allergies and immunology. NIH is an agency of the U.S. Public Health Service, U.S. Department of Health and Human Services.

Prepared by:
Office of Communications National Institute of Allergy and Infectious Diseases National Institutes of Health Bethesda, MD 20892
Public Health Service U.S. Department of Health and Human Services April 1995