How long can HIV go undetected?

Megan Souness Alphabiolabs

By Megan Souness, Technical Manager for Health Testing and Covid‑19 at AlphaBiolabs
Last reviewed: 12/12/2022

In this article, we discuss HIV, what it is, how long the virus can go undetected, and the different stages of HIV infection.

What is HIV?

Human Immunodeficiency Virus (HIV) is a virus that is transferred through bodily fluids including blood, vaginal fluids, and semen.

The virus weakens your immune system over time and, although there are some early symptoms you can look out for including fever, headache, tiredness or fatigue, loss of appetite, a sore throat and/or swollen lymph nodes, many people do not display any symptoms at all for weeks, months or even years.

This means that HIV is highly transmissible and is often passed on through sexual intercourse, by people who do not realise that they have the virus.

The virus is most commonly transmitted by having vaginal or anal sex, but it can also be transmitted through non-sexual contact, such as by sharing needles.

Mothers with HIV can also pass the virus on to their babies during childbirth or breastfeeding.

You can learn more about HIV by visiting

Order a Home HIV Test Kit Online

What are the symptoms of HIV?

Many people with HIV will experience flu-like symptoms 2-6 weeks after they are first infected.

The immediate period after a person has become infected with HIV is called acute HIV infection, while the six-month period after infection is referred to as primary HIV infection.

Some common symptoms of HIV include:

  • Sore throat
  • Fever
  • Rash on the body
  • Fatigue
  • Joint and/or muscle pain
  • Swollen glands

These symptoms can be easily misdiagnosed as a cold or flu, so it is important that you get tested if you suspect that your symptoms could be caused by HIV, particularly if you have recently engaged in unprotected sex or have used shared needles.

IMPORTANT: If you believe you have been exposed to HIV within the past 72 hours, you should seek PEP medication from your local sexual health clinic as soon as possible.

What are the different stages of HIV?

There are three stages to HIV infection.

Stage 1: Primary or acute HIV infection

The immediate period after a person becomes infected with HIV. During this phase, the virus spreads throughout the body and often causes flu-like symptoms such as fever, headache, and a rash.

This is because the immune system is trying to fight off the infection.

Stage 2: Clinical latency or chronic HIV infection

This is where an infected person does not show any symptoms of infection and may even feel relatively healthy.

However, even if someone has no symptoms, the virus is still replicating and causing damage to the immune system.

People who are aware that they are living with HIV may take antiretroviral treatment (ART), to help control the infection and they may remain in this chronic stage for decades. Taking ART also means that people have a very low viral load, both preventing the infection from worsening and hugely reducing the risk of transmitting HIV to sexual partners.

Stage 3: Acquired immune deficiency syndrome (AIDS)

Without treatment, chronic HIV infection will advance to AIDS. This can take 10 years but can be faster or slower depending on the person.

AIDS is the final stage of infection. This is where the cells of the immune system are depleted and struggle to fight off other infections.

People with AIDS usually experience the most severe illness because the immune system is no longer strong enough to manage disease and illness without medical intervention. However, new medicines mean it is now possible to recover from an AIDS diagnosis with treatment.

Most people with HIV who are diagnosed early enough and take antiretroviral treatment (ART) will not go on to receive an AIDS diagnosis.

This makes regular STI testing, including HIV testing, extremely important as it ensures that infections are detected as early as possible.

Related: How soon do STI symptoms appear?

How long can HIV go undetected? How long can I have HIV for without knowing?

If you become infected with HIV but do not test for it, or test too early, it may take a long time to receive a diagnosis.

This is because the initial symptoms, which may appear 2-6 weeks after you are first infected, are very similar to the flu and may only last 1-2 weeks.

After the acute HIV infection phase is over, you may enter the asymptomatic phase, where you experience no symptoms at all.

During the chronic (asymptomatic) phase of a HIV infection, you may not experience any symptoms for several years. This time frame will vary from person to person, but can last up to 10 years.

In the meantime, the virus will progressively damage your immune system.

According to the National AIDS Trust, 42% of people who were newly diagnosed with HIV in 2019 had chronic phase HIV infection, and people who are diagnosed late have, on average, been living with HIV for 3-5 years.

If HIV is left untreated for long enough, the immune system becomes so weakened that the infection progresses to stage 3, known as acquired immune deficiency syndrome (AIDS).

If the infection progresses to the AIDS stage and the infected person does not seek treatment, they are more likely to experience unpleasant and potentially life-threatening symptoms.

If you are sexually active, the best way to ensure you remain clear of any infections is to get tested for STIs regularly, including HIV.

Although there is no cure for HIV, if detected and diagnosed early, it is possible to treat the infection with antiretroviral drugs.

These drugs stop the virus replicating in the body, allowing the immune system to repair itself and ensuring the virus remains undetectable. When HIV is undetectable, the virus cannot be passed on to other people even while it remains in the body. This is known as undetectable = untransmittable (U=U).

If you are experiencing symptoms causing severe pain and discomfort or that require face-to-face examination, we advise you to contact your GP or local sexual health clinic as soon as possible.

IMPORTANT: If you believe you have been exposed to HIV within the past 72 hours, you should seek PEP medication from your local sexual health clinic before getting tested for HIV.

How does HIV cause disease?

Human Immunodeficiency Virus (HIV) infects the cells of the immune system by entering these cells and inserting its genomic material into the DNA of the infected person.

This causes the cells to replicate the viral DNA, producing more of the virus within the body.

The immune system is made up of many cells that are specialised in identifying foreign invaders in our bodies and dealing with these threats. Our immune systems are constantly on the lookout for threats to our health and can often fight off infection without a person knowing.

When a person has an infection, the immune system sends lots of different cells to the site of the infection to help kill the microorganisms responsible.

However, when a person is infected with HIV, the immune system does not work as well.

This is because HIV targets cells in the immune system which then begin to die, decreasing the number of immune cells available to help fight off illnesses.

Without diagnosis and treatment, HIV continues to replicate and deplete these specialised cells.

If HIV is left undiagnosed/untreated, the immune system depletes, making it much harder for the body to fight off infection. It is at this point that acquired immune deficiency syndrome (AIDS) develops.

Order a Home HIV Test Kit Online

How long do HIV symptoms last?

Symptoms of HIV will usually last 1-2 weeks after a person is first infected but can last longer in some people.

When the initial symptoms subside, further symptoms may not appear for many years, even though the virus is still replicating in the body and damaging the immune system over time.

After the primary infection phase, most people enter the asymptomatic HIV infection phase. This means that the infected person will not have symptoms, even though they are still infected with HIV.

Depending on the individual, a person can live for years in this asymptomatic phase.

Following this asymptomatic period, an individual who is untreated for HIV will enter the symptomatic HIV infection phase and start to become more seriously ill.

Symptoms experienced during this phase are usually more serious and unpleasant than those experienced during the acute/primary phase, and can include:

  • Weight loss
  • Chronic diarrhoea
  • Skin disorders
  • Night sweats
  • Recurrent infections
  • Life-threatening illnesses

If HIV is still left untreated at this stage, the infection can develop into acquired immune deficiency syndrome (AIDS), which is sometimes referred to as advanced HIV.

AIDS occurs when a person’s immune system has become significantly weakened by HIV. At this stage, the immune system does not work properly, making the individual more susceptible to infections.

People with AIDS also have an increased risk of developing some cancers.

How long does it take to detect HIV?

The length of time it takes to detect HIV depends on the person and the type of test used.

The window period for HIV – the amount of time from when a person is first infected to when the infection can be detected in a blood sample – is 4-12 weeks.

According to the NHS, a blood test is the most accurate way of detecting an HIV infection and gives results as early as one month post-infection.

A laboratory test using a blood sample looks for the presence of HIV antibodies that the body produces in response to the virus, and the p24 antigen, part of the HIV virus.

This means that for a test to be able to detect HIV, there needs to be enough circulating antibodies or HIV antigen (usually p24 antigen) in the body.

If a blood sample is collected too soon, the results of the test may not be as accurate, because it takes time for HIV antibodies or p24 antigen to show up in a blood sample.

If an infection is identified (the result is ‘positive’ or ‘reactive’), confirmatory tests are required to confirm the positive result. Following this, more tests may be carried out and HIV specialists will provide guidance on treatment options.

If a person takes an HIV test within the window period for the infection (4-12 weeks) and receives a ‘non-reactive’ result (i.e. negative), it is recommended that they take another test after the window period has ended (i.e. after 12 weeks) to be sure they are clear of any infection.

If you suspect there is a chance you have HIV, or have been exposed to HIV, you should seek medical advice immediately.

If you believe you have been exposed to HIV within the past 72 hours, you should seek PEP medication from your local sexual health clinic as soon as possible.

How can I get tested for HIV?

You can access HIV testing in person via your GP or local sexual clinic, and many healthcare services will usually offer HIV testing as standard before 10 weeks of pregnancy.

This is because HIV can be passed on from mothers to their babies during pregnancy.

Alternatively, you can order a home HIV test online.

For this type of test, you will be sent everything you need to collect your own blood samples and return them to a testing laboratory for analysis.

An AlphaBiolabs home HIV test is available for just £29 and will tell you whether you have HIV-1 and HIV-2 markers, as well as the p24 early detection marker, using a finger prick blood sample.

Please note, if you receive a Reactive result from an AlphaBiolabs HIV test, you MUST contact your GP or local sexual health clinic for confirmatory testing, further guidance and treatment options as soon as possible.

You must be at least 16 years of age to purchase a home STI test kit from AlphaBiolabs.

If you believe you have been exposed to HIV, it is important that you do not wait to be offered a test. It is recommended that you visit a clinic or order a test kit online as soon as possible.

If you believe you have been exposed to HIV within the past 72 hours, you should seek PEP medication as soon as possible.

Order an STI test kit

At-home STI testing you can trust, from just £29.

Megan Souness, AlphaBiolabs

Megan Souness

Technical Manager for Health Testing at AlphaBiolabs

Megan joined AlphaBiolabs in 2020 and holds the role of Technical Manager, playing a fundamental part in the research and development of new health testing services at AlphaBiolabs.

In addition to developing new services, Megan oversees the day-to-day processes in the Health Laboratory, managing the in-house validation and training of all new workflows, and ensuring the lab operates to the highest possible quality technical standards.

During her time at AlphaBiolabs, Megan has played a key role in the development and launch of the company’s health testing services, including the introduction of a full suite of at-home STI tests, and the progression of the laboratory to ISO 15189 standards.

Megan holds a BSc in Biochemistry, an MSc in Biological Sciences, and is a member of the British Association for Sexual Health and HIV (BASHH).

2 thoughts on “How long can HIV go undetected?

  1. I was exposed to hiv on 10th April last month,,then 4weeks passed i tested myself i was still negative but i dont know what i should do now,,am scared

    1. We would recommend further testing at 12 weeks.
      Testing at 4 weeks will identify 90-95% of HIV positive cases but testing at 12 weeks will provide much greater assurance of a HIV negative results, as 99.9% of infections will be identified.

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