HIV stands for human immunodeficiency virus. Most people get HIV when they have unprotected sex or share needles with someone who has the virus.

The virus attacks and weakens your immune system, which is your body's natural defense against infection. HIV infects certain white blood cells called CD4+ cells. If too many of these cells are destroyed or weakened, your immune system is less able to fight infection and disease.

HIV infection can lead to AIDS (acquired immunodeficiency syndrome). People with AIDS have a low number of CD4+ cells and get infections and some cancers that rarely occur in healthy people. These can be deadly.

If HIV is diagnosed before it becomes AIDS, medicines can help keep your immune system strong and healthy. With treatment, many people with HIV are able to live long and active lives.

A combination of three or more antiretroviral medicines, called highly active antiretroviral therapy (HAART), is the main treatment for HIV. It can slow the rate at which the virus multiplies, prevent AIDS, and keep your immune system healthy.

The goal of treatment is to reduce the amount of virus in your body so that it can no longer be detected in your blood.

There are several medicines that are most often combined to treat HIV. They are sorted into five groups:

• Nucleoside/nucleotide reverse transcriptase inhibitors, such as tenofovir, emtricitabine, and abacavir
• Nonnucleoside reverse transcriptase inhibitors (NNRTIs), such as efavirenz, nevirapine, and etravirine
• Protease inhibitors (PIs), such as atazanavir, ritonavir, and darunavir
• Fusion and entry inhibitors, such as enfuvirtide and maraviroc
• Integrase inhibitors, such as raltegravir

The U.S. National Institutes of Health recommend one of the following programs for people who begin treatment for HIV:¹

• Efavirenz + tenofovir + emtricitabine
• Ritonavir-boosted atazanavir + tenofovir + emtricitabine
• Ritonavir-boosted darunavir + tenofovir + emtricitabine
• Raltegravir + tenofovir + emtricitabine

You can now get some of these medicines combined into one pill. So you may take 1 to 4 pills a day. Medicines can help stabilize and increase the number of CD4+ cells in your body. And they can prevent AIDS.

HAART doesn't cure HIV. But people who take these medicines as prescribed:

• Avoid getting AIDS, or recover from the symptoms of AIDS and enjoy a return to better health.
• Develop fewer conditions, such as pneumonia and certain types of cancers, which are common in people whose immune systems are weak. These are called opportunistic infections.
• See a major drop in the amount of virus in their body, often to a level where it can no longer be detected in their blood.
• Have a stable or increasing CD4+ cell count.

For the medicine to work, you need to take it every day. If you can't take your medicine as prescribed and you miss doses, HIV may become resistant to the medicine and harder to treat.

Antiretroviral medicines can have side effects that are sometimes serious. If you have side effects, talk to your doctor about ways to reduce them. You may be able to change the way you take the medicines or change to other medicines that have fewer side effects for you. Most people can find an HIV treatment combination that works for them. Be sure you keep taking your medicines, because they help keep the virus under control and your immune system healthy.

If you can't take your medicine as prescribed and you miss doses, HIV may become resistant to the medicine and harder to treat.

Some side effects, such as nausea, may improve when your body adjusts to the medicines. If you have problems taking your medicines, talk with your doctor. There are medicines you can take to treat the side effects.

Side effects of some antiretroviral medicines may include:

• Nausea and vomiting.
• Diarrhea.
• Fever.
• Fatigue.
• Headache.
• Dizziness.
• Belly pain.
• Trouble sleeping.

Certain antiretroviral medicines may also cause more serious medical problems, such as a buildup of acid in your blood, and changes in the way your body stores fat and uses sugar.

Treatment with antiretroviral drugs is recommended:^{1, 2, 3}

• When your CD4+ cell count drops below 500 cells per microliter, to help keep your immune system healthy and to prevent AIDS.
• If your CD4+ cell count is greater than 500, especially if you are at risk for other health problems.
• If you're pregnant. Medicines can help keep your developing baby from getting HIV.
• If you have symptoms of HIV or AIDS, no matter what your CD4+ cell count is.
• If you also have hepatitis B, which is caused by a virus that attacks the liver.

You may also want to start HIV treatment if your sexual partner does not have HIV. Treatment of your HIV infection can help prevent the spread of HIV to your sexual partner.^{3, 4}