About STIs

Below is a list of the sexually transmitted infections (STIs) we can test for, and some information about each of them.


Chlamydia is one of the most common STIs in the UK. Most people with chlamydia do not notice any symptoms and do not know they have it but are still able to pass it on to a sexual partner. Untreated chlamydia can lead to pelvic inflammatory disease, which in turn can cause infertility. Chlamydia can be treated easily with a course of antibiotics and can be detected in STI tests around 2 weeks after sex. If you live in England, are under 25 and are sexually active, it is recommended that you get tested for chlamydia every year, or when you change sexual partner.


Gonorrhoea is a bacterial sexually transmitted infection. It can be treated with a course of antibiotics, but if left untreated, it can cause serious health complications. About 1 in 10 infected men and 5 in 10 infected women will not experience any obvious symptoms but can still pass it on to a sexual partner, so getting tested is important. Gonorrhoea can be detected in STI tests at around 2 weeks after sex.


HIV (human immunodeficiency virus) is a virus that damages the cells in your immune system and weakens your ability to fight everyday infections and disease. It is often sexually transmitted but can also be passed on through sharing infected needles and from mother to baby during pregnancy and breastfeeding. It is now very easy to manage with the use of lifelong antiviral treatments for those who have the infection.

Most people experience a short flu-like illness 2 to 6 weeks after becoming infected with HIV. After these symptoms disappear, HIV may not cause any more symptoms for many years. This means many people with HIV do not know they're infected. Anyone who thinks they could have HIV should get tested.

Trichomonas vaginalis

Trichomonas Vaginalis (TV) is a tiny protozoan that can cause an STI. It only causes symptoms in around half of people who have it and men rarely have symptoms. Testing for trichomonas can prevent you from passing it to a partner, even if you have no symptoms of your own. TV is treated with a course of antibiotics.

Symptoms include abnormal vaginal discharge that may be thick, thin or frothy and yellow-green in colour, with an unpleasant fishy smell. They can also include soreness, swelling and itching around the vagina or the head of the penis or foreskin, and pain or discomfort when passing urine or having sex.

Syphilis (treponema pallidum)

Syphilis is a bacterial STI. It is still quite rare, but the number of syphilis cases in the UK has risen sharply in recent years. As well as being passed on through sex, syphilis can also be passed on through sharing infected needles and from mother to baby during pregnancy. The symptoms of syphilis are not always obvious and some people with syphilis have no symptoms. It is important to get tested and treated as soon as possible if you think you might have syphilis, as it can cause serious problems if it's left untreated. It can usually be cured with a short course of antibiotics.

Mycoplasma Genitalium

Mycoplasma Genitalium (MG) is a small bacterium that can infect both men and women, passed through sexual contact or activity. Almost all MG infections are symptom free, lasting for months to years, and cause no harm to the human body. However, if it does cause symptoms, these can be similar to other STIs, such as pain while urinating, pain during sex, or increased vaginal or penile discharge. If untreated, it can lead to further complications such as Pelvic Inflammatory Disease.

Hepatitis B

Hepatitis B (HBV) is a virus that affects the liver and can cause short-term or long-term infection. In people who develop a long-term infection with HBV they can go on to develop cirrhosis and liver failure. It can be passed on through sexual activity, and also through sharing needles and to the baby during pregnancy. It often does not cause any obvious symptoms in adults, and typically resolves in a few months without treatment. HBV is less common in the UK than other parts of the world, but certain groups are at an increased risk. The best way to prevent getting HBV is to get vaccinated. Since 2017, HBV vaccination has been part of the routine immunization schedule for all children in the UK.

Hepatitis C

Hepatitis C is caused by the hepatitis C virus and is the most common type of viral hepatitis in the UK. Hepatitis C often does not have any noticeable symptoms until the liver has been significantly damaged, so many people are unaware they're infected. In most cases, it stays in the body for many years. This is known as chronic hepatitis C and can cause cirrhosis and liver failure.

Symptoms include flu-like symptoms, tiredness, loss of appetite, tummy (abdominal) pain and feeling sick. The only way to know for certain if these symptoms are caused by hepatitis C is to get tested.