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If you have a symptom that you think is due to a sexually transmitted illness - STI - or if you have no symptoms but are worried you have an STI, you should contact a health professional.

How do you find out if you have an STI?

Dr Rosemary Leonard MBE

This depends on which sexually transmitted infection (STI) is involved. Conditions such as anogenital warts and pubic lice are usually diagnosed during an examination by a doctor and may not need any laboratory tests to confirm the diagnosis.

Testing for trichomonas, chlamydia and gonorrhoea usually involves taking 'swabs'. A swab is a small ball of cotton wool on the end of a thin stick, rather like a long cotton bud - see image below. It can be gently rubbed in various places to obtain a sample of mucus, discharge, or some cells. These samples can be taken from the vagina, penis, throat and/or back passage (rectum). You may be able to take the sample yourself in many situations.

The sample can then be looked at under a microscope and sent away to the laboratory for testing. A test kit with a swab sample can also detect thrush, bacterial vaginosis and various other germs (bacteria) which are not STIs.

Sterile swab testing kit

Sterile swab
Whispyhistory, CC BY-SA 4.0, via Wikimedia Commons

By Whispyhistory, CC BY-SA 4.0, via Wikimedia Commons

Chlamydia can also be detected using samples of urine.

HIV, hepatitis B, hepatitis C and syphilis are usually tested for using a blood sample which is sent to a laboratory for analysis.


of people would visit their GP if they they had an STI. 37% would visit a sexual health clinic.

Source: Patient Sexual Health Survey

If you have a symptom that you think is due to an STI, or if you have no symptoms but are worried you have caught an STI, you should see a health professional. You can:

  • See your own GP. Your GP can give advice and may examine you. However, if your GP suspects that you may have an STI, in the UK he or she is likely to refer you to a genitourinary medicine (GUM) clinic. Some GPs may do tests and manage the situation without a referral to a GUM clinic; or
  • Go to a GUM clinic directly. You do not need a referral from your GP to go to a GUM clinic; or
  • Check to see if you can send your own sample to a laboratory by post. This service may be offered by the NHS to certain age groups, or by private companies via the internet.

Until you are checked out, and treated if necessary, you should not have sex. This is to prevent you passing on any infection.

GUM clinics are special sexual health services in the UK that help people who have, or may have, an STI or certain other problems with their genitals or urine system. Staff in most GUM clinics include doctors, specially trained nurses and sexual health advisors. Many GUM clinics are attached to hospitals but some are based in community settings. Other names that have been given to GUM clinics include STI clinics, STD clinics (STD is short for sexually transmitted disease), VD clinics (VD is short for venereal disease), and sexual health clinics.

Most STIs are diagnosed and treated at GUM clinics. Some people are diagnosed with an STI in another type of clinic - for example, at a GP surgery, or in a family planning clinic. In these situations you are still likely to be referred to a GUM clinic for treatment, and for any follow-up or counselling that may be required.

Anyone can attend a GUM clinic. You do not have to be aged over 16. If you want, you can take a friend or relative with you when you attend. You can go to any GUM clinic - it does not have to be the one nearest to you.

This may vary depending on the clinic. For many, you do not need to forward book an appointment but can just turn up. However, you may have to wait some time to be seen depending on how busy it is. It may be best to give the clinic a call in advance to check if you can just turn up without an appointment, and the times the clinic is open. Some clinics can become quite busy.

If you suspect that you have an STI, then contact your local GUM clinic or see your GP. In the UK you can go to the local GUM clinic without a referral from your GP. You can ring your local hospital or your GP and ask where the nearest clinic is. Local and national information is also available on the internet - for example, from the NHS 'Find a clinic' service - link provided in Further Reading section below.

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When you arrive at a clinic you will have to register. You will be asked for your name, address, date of birth, contact telephone number and the name of your GP. This information is treated confidentially. The clinic will not contact you at home or contact your GP without your permission. Also, any records from GUM clinics will not go on your main medical record without your permission.

However, if you have a concern, you do not have to give any details. You can even give a false name. The important thing is that whatever name you do use, you should use the same name for any follow-up appointment, to avoid any confusion; for example, when you return for the result of any tests. To help identify you as the correct person for any follow-up, you will be given a card with your clinic number on it, which you should bring back to any follow-up appointment.

Initial assessment

You will be seen initially by a doctor, a specially trained nurse or a sexual health adviser. They will ask you some questions to try to assess the situation and to determine what tests (if any) you may need. You may find some of the questions quite personal but they are all necessary to ensure the correct diagnosis and treatment are given.

Examples of questions that you may be asked include:

  • What symptoms and/or concerns do you have?
  • How many people have you had sex with in the last few weeks and were they male or female?
  • What type of sex have you had - vaginal, oral, anal?
  • Have you previously had an STI?
  • What is the state of your general health?
  • Do you take any regular medication?
  • Do you have any allergies?

If you are a woman you may be asked about the date of your last period and whether there is a chance that you may be pregnant, as this might affect treatment options. You may also be asked about whether you have had a cervical smear test. This test looks for human papillomavirus (HPV) which is known to be a major factor in the development of cervical cancer. This is sensible as part of a general sexual health check.

After the initial assessment you will be advised what will happen next. You will normally be examined and at the same time some tests may be taken.

A doctor will usually examine you. You can ask for a male or female doctor, but you may have to return at a different time (or even to a different clinic) if a doctor of a particular sex is not currently available. The examination includes looking carefully at your genitals for signs of unusual discharge, redness, lumps or ulcers. The doctor may also feel the tops of your legs (your groins) to check for enlarged or tender glands called lymph nodes. If necessary, the doctor may also do a general examination to check on your general health.

In women, your doctor may also examine your vagina and womb (uterus) by gently inserting a lubricated, gloved finger.

Men may have their testicles (testes) examined.

After the examination is complete your doctor may also take some tests.


The way in which tests are done can vary from clinic to clinic; the following is a general guide.

After the examination of the outside of the genitals the doctor will ask your permission to insert a speculum. This is a plastic or metal device which is also used to take a cervical smear when screening for cervical cancer. It helps the doctor to see the neck of the womb (the cervix) and allows some samples to be taken.

The doctor will usually warm the speculum if it is metal and cover the tip in lubricating jelly. Once the speculum has been inserted it is slowly opened and held in place by a catch. The doctor will then look closely at the walls of the vagina for any discharge or redness. A swab is usually taken from the vagina and from the cervix. A swab is a small ball of cotton wool on the end of a thin stick, used to collect samples. The doctor will then slowly remove the speculum.

After this has been done a small plastic spatula may be used to take cells from the urethra (the opening which allows urine to pass from the bladder to the outside of the body). This may feel a little scratchy. Depending on the information you have given initially it may also be necessary to take swabs from the back passage (rectum) or the throat. After all the swabs are taken you will be able to get dressed. You may be asked to provide a urine sample.


After the examination of the outside of the genitals the doctor will ask for your permission to insert a swab into the urethra. This may feel a little uncomfortable but most people do not find it painful. Depending on the information you have given initially it may also be necessary to take swabs from the rectum or the throat.

If there is any possibility of infections that may affect the rectum, your doctor may ask your permission to examine this area more closely. Sometimes this is done using a proctoscope. This is a small tube, usually made of plastic, that makes it possible to see inside the rectum. After all the swabs are taken you will be able to get dressed. You may be asked to provide a urine sample.

Men and women - blood tests

A sample of blood from a vein may be taken. This is mainly used to test for syphilis, hepatitis B, hepatitis C and HIV. Sometimes you may be advised to delay having a blood test. For example, following an initial infection of HIV it can take several weeks for a blood test to become positive. So, for example, if within the previous few days you had sex with someone who is HIV-positive, you may be advised to wait several weeks to have a blood test to see if you have become infected.

If you are seen at your GP surgery, the swabs and blood tests will be sent to a laboratory for further testing. Your doctor will advise you about when the test results will be available; this can take up to a fortnight and are usually sent to you via text message.

If you are seen in a GUM clinic some of your results may be available on the same working day of your test.

Your doctor or nurse will take the swabs and smear them on to special slides. This allows him/her to look at the cells taken from the swabs under the microscope. Some germs (bacteria) that cause infections can be seen in the cells you have provided by having swabs done. For example, the bacteria that cause gonorrhoea can sometimes be identified by looking through a microscope. This may mean you are given a positive result on the day, if you have the infection.

However, even though the bacteria can be detected under the microscope, they are not always seen, even if they are present. To make sure the test result is reliable, the sample you give is put into a special pot. This pot also contains a substance that allows the bacteria to grow. The pot, known as a plate, is then put into an incubator allowing any bacteria present to grow. The plates are then checked to see if any bacteria which cause STIs have grown. It takes a while for the bacteria to grow; this is why you may be asked to check back with the clinic for more results in a few weeks' time. Trichomonas can also be seen under the microscope.

The results of tests for chlamydia and blood tests for syphilis, hepatitis B and hepatitis C are usually not available on the same day.

Some clinics offer same-day HIV testing. This means you get the result of the test on the day your blood sample is taken. Most clinics ask you to make an appointment for this service, as it may only take place at certain times.

The swabs that are taken sometimes show other infections which are not considered to be STIs. This includes bacterial vaginosis and thrush. These infections can also be seen by looking at the samples you give under the microscope.

After your doctor or nurse has checked your samples they will call you back into the consulting room. They will give you any results available from checking the cells under the microscope.

You will also be advised about how long it should take to get any other test results back to the clinic. Each clinic has a different method of giving test results. Some may ask you to come back or ring the clinic; some work on a 'no news is good news' policy. It is important you understand how you will get your results and that the contact information you give is reliable.

If you have a positive test result for an STI on the day of your attendance at clinic you will be given treatment and advice on the same day. You will also be asked to speak to a sexual health advisor to help trace any of your sexual partners who may have come into contact with the infection.

If the test results come after you have left the clinic you will be given advice about what to do next when you receive your result.

The treatment that you will be offered depends on what STI is found. For example, a short course of antibiotic medicine can usually clear away chlamydia, gonorrhoea, syphilis and trichomonas. A cream or lotion can clear pubic lice and scabies. Topical treatments can usually clear most anogenital warts. Treatments for genital herpes, hepatitis B, hepatitis C, and HIV are more involved and complex. You will be given advice about what treatment options you have and given time to ask questions.

If you are prescribed antibiotics then it is important to finish the full course of tablets, or else the infection may not be fully cleared. If you develop side-effects then seek advice from the GUM clinic or from your GP surgery as to what to do. Do not simply stop taking the medication. For some infections you will be asked to return after a course of treatment to check that the infection has gone.

Note: do not have sex again until the time advised by the clinic. Depending on the infection, this may be for a certain length of time after treatment is finished or it may be until you are given the 'all clear' from a repeated test. The aim is to prevent you from passing on the infection to others.

Mycoplasma Genitalium (Mgen)

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Further reading and references