Leaving sexually transmitted infections untreated can lead to an array of problematic health complications.

Even though many STIs don’t necessarily cause noticeable symptoms it is still important to get tested and treated.

Here we will discuss the most common complications and what they might mean for your general health in the long term.

Pelvic Inflammatory Disease (PID)

PID is a common infection contracted by women and is caused by bacteria which progresses from the vagina or cervix to the upper genital tract.

Infected women can experience pain around the lower abdomen, discomfort during sex or urination, heavy periods, bleeding inbetween periods, unusual discharge, a fever or nausea and vomiting. It can be caused by untreated chlamydia or gonorrhoea infections.

According to official statistics, 10-15 per cent of women with chlamydia who do not seek treatment go on to develop PID, which can also be linked to cases of female infertility.


Failure to treat STIs can make both men and women infertile.

A couple might be diagnosed as infertile after one whole year of failing to conceive.

Female infertility caused by STIs may occur due to damage to the fallopian tubes.

Male infertility can be the result of an infection in the testes often attributed to chlamydia. This can result in a reduction in the number of sperm being produced making it more difficult to conceive.

Studies have found that sexually active adolescents and young adults aged between 15-24 years are the group most at risk of contracting STIs, with half of all newly diagnosed STIs falling into this age range.

In the short term, this particular age group might not think about the impact that infertility can have on their future. However, it should be noted that infertility can lead to relationship difficulties and mental health problems.

Miscarriage and Ectopic Pregnancy

Some STIs can cause permanent damage to the female reproductive organs.

This can create problems when trying to conceive, as detailed above, or during pregnancy.

PID can lead to scarring which makes it difficult for fertilised eggs to pass from the ovaries into the womb. This may increase the chances of the egg getting stuck in the fallopian tube.

If the egg starts to develop outside of the womb this is known as an ectopic pregnancy which can lead to immediate health complications and even be fatal.

According to a study by the National Centre of Biotechnology Information (NCBI) around 40 per cent of ectopic pregnancies can be attributed to infectious factors, including STIs.

The bacteria from some sexually transmitted infections such as chlamydia can cause the foetus to die in the uterus. A primary infection of genital herpes contracted during pregnancy can also cause miscarriage.


Epididymo-orchitis is a condition that some men may contract if they do not access STI treatment.

Epididymitis refers to swelling found in part of the testis involved in making sperm. Orchitis is the clinical name given to swelling of the testis.

This condition is most commonly caused by STIs such as chlamydia and gonorrhoea. These two STIs infect the urethra but the bacteria can also progress into the testes if left untreated.

As outlined in a paper commissioned by the British Association for Sexual Health and HIV (BASHH) some rare cases of epididymo-orchitis can lead to a reduced sperm count which can reduce fertility.

Increased Risk of HIV

Those who fail to seek treatment for STIs increase their risk of becoming infected with HIV if they continue to have unprotected sex. According to the Palo Alto Medical Foundation (PAMF) women infected by chlamydia are up to five times more likely to contract HIV if exposed.

Therefore the treatment of STIs is important in the prevention and reduction of HIV. HIV causes serious damage to the body’s natural immune system, eventually shutting it down completely. There is no cure for HIV and symptoms have to be closely managed throughout a person’s life.

Spread of Infection

If you leave an STI untreated and have unprotected sex there is a high possibility that you will spread the infection to your sexual partner. Women can also pass some STIs onto their baby during childbirth which can cause complications.


A syphilis infection can progress through three stages if left untreated.

Stages one and two can cause unpleasant symptoms, however, the third stage can be extremely dangerous and cause organ failure, stroke, paralysis, blindness, deafness, heart disease and dementia.

How to Avoid STI Complications

The possible complications caused by leaving STIs untreated are numerous and in some cases extremely harmful to the infected person’s general health.

STI treatment should be started as soon as possible to reduce the chances of becoming infertile. It is important to remember that many STIs can be asymptomatic and initially present no obvious cause for concern.

Even though typical STI symptoms might not be present there is still a possibility that an infection has been contracted. Therefore it is important for anyone who has sexual contact or intercourse without protection to be regularly screened.

Page last reviewed:  19/07/2016