It depends on which sexually transmitted infection (STI) you have.
Symptoms can develop within a few days or weeks, but sometimes they do not appear until months or even years later.
Often there are few or no symptoms and you may not know you have an STI.
If there's any chance you could have an STI, go to a sexual health clinic or GP for a free and confidential check-up.
Chlamydia
Symptoms usually appear after 1 to 3 weeks but can start much later. Symptoms include:
- discharge from the vagina or penis
- pain when peeing
- vaginal bleeding between periods or after sex
- pelvic pain in women
- testicular pain in men
About 50% of men and 70% of women who are infected do not have any symptoms.
Find out more about chlamydia.
Genital herpes
Symptoms can appear after 4 to 7 days but might not start until months or years later. Symptoms include:
- small, painful blisters around the genitals
- pain when peeing
- a tingling or itching around the genitals
- discharge from the vagina or penis
- flu-like symptoms such as a high temperature or headache
Most people do not have any symptoms when first infected.
Find out more about genital herpes.
Genital warts
If genital warts appear, symptoms could start from 3 weeks to many months or even years after contact with the virus that causes them.
Symptoms include small, fleshy growths or bumps on the genitals or around the anus – these are usually painless, but may be itchy.
Most people with the virus that causes genital warts do not develop obvious warts.
Find out more about genital warts.
Gonorrhoea
Symptoms usually appear within 2 weeks of being infected but could start much later. They include:
- green or yellow discharge from the vagina or penis
- pain when peeing
- lower tummy pain
About 10% of men and 50% of women who are infected do not have any symptoms.
Find out more about gonorrhoea.
Pubic lice
It can take several weeks before any symptoms of pubic lice appear. Symptoms are the same for men and women, and include:
- itching in the affected areas, especially at night
- inflammation and irritation caused by scratching
- black powder (lice droppings) in your underwear
- blue spots or small spots of blood on your skin, such as on your thighs or lower tummy (caused by lice bites)
Find out more about pubic lice
Scabies
Symptoms of scabies can take up to 6 weeks to appear if you have never had them before. It may only take up to 4 days if you have had scabies before. Symptoms include:
- itching in affected areas such as around the genitals, waist, fingers or bottom (usually worse at night)
- a spotty red rash
Find out more about scabies.
Syphilis
Symptoms usually appear after 2 to 3 weeks but could start earlier or much later. They include:
- one or more small painless sores or ulcers on the genitals
- a blotchy rash, white patches in the mouth and flu-like symptoms that may follow a few weeks later
Symptoms are often not obvious and may come and go.
Find out more about syphilis.
Trichomoniasis
Symptoms usually appear within 4 weeks but could start months later. They include:
- discharge from the vagina or penis
- pain when peeing
- itchiness or discomfort around the opening of the vagina
About 50% of men and women who are infected do not have any symptoms.
Find out more about trichomoniasis.
HIV
The first symptoms may appear after 2 to 6 weeks. They can include:
- flu-like symptoms, such as a high temperature (fever), sore throat, headaches, and achy muscles or joints
- a red rash on the body
Not everyone gets these symptoms, but in people who do they usually last 1 to 2 weeks.
After the symptoms disappear, you may not have any further symptoms for many years, even though the infection remains in your body.
Find out more about HIV.