According to the Centers for Disease Control and Prevention (CDC), roughly 1.1 million Americans are living with HIV. More than 15 percent of people living with HIV don’t know they have it. In addition to not getting the treatment they need, they can unknowingly transmit the virus to others. In fact, 30 percent of new HIV cases are transmitted by people who are undiagnosed.

The CDC’s 2006 recommendations for HIV testing advise healthcare professionals to provide routine screenings for HIV as a part of standard care. HIV screenings should occur at least once in a lifetime for adults, and regularly for people with ongoing risk for acquisition. But some providers aren’t implementing these guidelines. Many Americans have never been tested for HIV.

Anyone who hasn’t been tested for HIV should consider asking their healthcare provider for a test. They can also seek free and anonymous HIV testing at a nearby clinic. Visit the CDC’s GetTested website to find a local testing site.

Routine HIV testing should be provided in all healthcare settings, advises the CDC. People engaging in behaviors that put them at an increased risk for HIV should be tested at least once a year.

Known risk factors include:

  • having multiple sexual partners
  • engaging in sex not protected by condoms
  • having partners with HIV
  • intravenous drug use

HIV testing is also recommended:

If a person has contracted HIV, early detection and treatment can improve their frame of mind, lower their risk of disease progression, and prevent the development stage 3 HIV, or AIDS. It can also reduce their risk of transmitting the virus to other people.

People who know that they’ve been exposed to HIV should seek care as soon as possible. In some cases, if they’re treated within 72 hours, their healthcare provider may prescribe post-exposure prophylaxis (PEP). These emergency medications may help reduce their chances of contracting HIV after they’ve been exposed to it.

A number of different tests can be used to check for HIV. These tests can be performed on blood samples or saliva samples. Blood samples can be obtained via an in-office finger prick or a blood draw in a laboratory.

Not all tests require a blood sample or a visit to a clinic. In 2012, the U.S. Food and Drug Administration (FDA) approved the OraQuick In-Home HIV Test. It’s the first rapid test for HIV that can be performed at home.

If a person thinks they’ve contracted HIV, it can take anywhere from one to six months after transmission for a standard HIV test to produce positive results. These standard tests detect antibodies to HIV rather than the virus itself. An antibody is a type of protein that fights off pathogens.

According to Avert, third-generation HIV tests — which are ELISA tests — can only detect HIV three months after exposure to the virus. This is because it generally takes three months for the body to produce a detectable number of antibodies.

Fourth-generation HIV tests, which look for antibodies and the antigen p24, can detect HIV one month after transmission. Antigens are substances that cause an immune response in the body.

According to Columbia University’s Go Ask Alice!, 97 percent of people with HIV produce a detectable number of antibodies within three months. Although it may take six months for some to produce a detectable amount, this is rare.

If a person thinks they’ve been exposed to HIV, they should tell their healthcare provider. A viral load test that directly measures the virus can be used to detect whether someone has recently acquired HIV.

If a person has received an HIV diagnosis, it’s important for them to monitor their condition on an ongoing basis. Their healthcare provider can use several tests to do this. The two most common measures for assessing HIV transmission are CD4 count and viral load.

CD4 count

HIV targets and destroys CD4 cells. These are a type of white blood cell found in the body. Without treatment, the CD4 count will decrease over time as the virus attacks the CD4 cells. If a person’s CD4 count decreases to fewer than 200 cells per cubic millimeter of blood, they’ll receive a diagnosis of AIDS.

Early and effective treatment can help a person maintain a healthy CD4 count and prevent the development of AIDS. If treatment is working, the CD4 count should remain level or increase. This count is also a good indicator of overall immune function.

If a person’s CD4 count drops below particular levels, their risk of developing certain diseases increases substantially. Based on their CD4 count, their doctor may recommend prophylactic antibiotics to help prevent these infections.

Viral load

Viral load is a measure of the amount of HIV in the blood. When a person’s viral load is low or undetectable, they’re less likely to develop AIDS or experience its associated immune dysfunction.

A person is also less likely to transmit HIV to others when their viral load is undetectable. If a person is taking their medication consistently and the virus is undetectable, they’re considered unable to transmit the virus to a partner.

A healthcare provider can measure the viral load to monitor the effectiveness of HIV treatment and the status of the disease. Effective treatment should reduce the viral load to undetectable levels. If a person maintains an undetectable viral load, they’re unlikely to develop AIDS.

Drug resistance

A healthcare provider may also order tests to learn if a strain of HIV is resistant to any medications used in treatment. This can help them decide which anti-HIV drug regimen is most appropriate.

Other tests

A healthcare provider may also use other tests to monitor someone for common complications of HIV or side effects of treatment. For example, they may perform regular tests to:

They may also perform physical exams and tests to check for other illness or infections associated with HIV or AIDS, such as other STIs, urinary tract infections (UTIs), or tuberculosis. A CD4 count below 200 cells per cubic millimeters isn’t the only sign that HIV has progressed to AIDS. AIDS can also be defined by the presence of certain opportunistic illnesses or infections, including:

If a person has received an HIV diagnosis, it’s important for them to monitor their health closely and report any changes to their healthcare provider. New symptoms may be a sign of an opportunistic infection or illness. In some cases, it may be a sign that their HIV treatment isn’t working properly or that their condition has progressed.

Early diagnosis and effective treatment can improve their frame of mind and lower the risk of HIV progression.