Reviewed June 2019

Is it because I had sex? The truth about what causes cystitis

Is it because I had sex- The truth about what causes cystitis 1200400

Most women will be familiar with the symptoms of cystitis and may have had to seek medical treatment for the condition at least once before. Some women may get cystitis regularly, with many finding they are particularly susceptible after having sex. But is there really much you can do to prevent it, and what actually causes it?

Simply put, cystitis is an inflammation of the bladder. The most common cause of cystitis is infection and it is due to bacteria, normally from the bowel, entering up through the urethra into the bladder. Between 70-90% of cystitis cases are caused by a bacteria called Escherichia coli (E. coli).1 E. coli does not normally cause any harm in the bowel but it can cause infection if it gets into other parts of the body.

The condition is more common in women than men because women have shorter urethras (the passage that runs from the bladder to the urinary opening) and a woman’s urethra is closer to the anus, which makes it easier for bacteria to reach the bladder.

Unfortunately, there is actually very little evidence that any lifestyle change can really help cure or prevent cystitis.2 Therefore, it may be important just to maintain good general hygiene and have a healthy lifestyle in order to avoid infection and help the immune system fight infection when it occurs. Despite this, there are plenty of myths surrounding cystitis, as well as some common situations in which you will be at higher risk of contracting it. We’ve looked at these to help you separate fact from fiction and understand what changes you can make to help prevent infection.

Common myths debunked

Traditionally, it has been recommended that women drink plenty of water and urinate more often to “flush” out bacteria, both as a preventative measure and a cure. However, there is no evidence that this makes any difference. Similarly, the advice for women to wipe from front to back after peeing to avoid bacteria travelling towards the urethra has not been proven to be effective. This being said, following these recommendations won’t do any harm.

Using plain, unperfumed bubble bath, having showers (so reducing contact time between cleaning agents and skin), and wearing cotton, non-tight underwear may only be useful if this has been found to be a particular irritant to the individual, rather than advisable for all.

Drinking cranberry juice or capsules on a regular basis was believed to prevent cystitis because cranberry juice contains substances that stop bacteria from sticking to the bladder wall. But a large study collecting data from 24 studies, with 4,473 participants, reported that cranberry juice did not appear to have significant benefit in preventing urinary tract infections.3

Situations which may make you more susceptible

Some conditions which allow bacteria to enter the bladder make cystitis more likely, but not everyone will get cystitis from them. Naturally, bacteria are not allowed to overgrow in the bladder because the bladder lining and mucus secretions prevent bacteria from multiplying. If these barriers are compromised then infection can result. Because of this, the actual situations in which your risk of cystitis has been proven to be increased are outlined below.

Having sex

During sex, bacteria may be transferred into the urethra via your partner’s fingers or penis, and this can cause cystitis. There may be slight damage to the urethral lining during sex that allows bacteria to stick and multiply. This is even more likely if the vagina is dry. Going to the toilet after sex may help get rid of bacteria that may be in the urethra and bladder, thus preventing cystitis. Having said this, not going to the toilet after sex doesn’t mean you will definitely get cystitis.

If the vagina is dry, using vaginal jelly during sex can help reduce the likelihood of getting cystitis. For some women, if cystitis triggered by sex is a frequent problem, your GP may prescribe a single dose of antibiotics to be taken within a couple of hours after sexual intercourse.


Using condoms is not known to prevent cystitis and using diaphragms and spermicides can actually make cystitis more likely because the normal mucus around the vaginal area is altered: “good” bacteria are killed, leaving infectious bacteria to grow.4 See your GP or practice nurse for advice about contraception if you are getting cystitis repeatedly and are using diaphragms or spermicides.

Urinary catheter

People who use any urinary catheter (a plastic tube inserted into the urethra to drain urine), whether intermittent or permanent, have a higher chance of cystitis because changing a urinary catheter can damage the lining of the urinary tract, and this may encourage infection. In some cases, the bacteria may even enter the bloodstream and cause septicaemia, a blood infection, which is serious.

People who use a catheter and are at high risk of serious infections, for example if they are known to have a weakened immune system or have had previous serious infections, may receive antibiotics when their catheter is changed. Everyone who uses intermittent or permanent urinary catheters should be vigilant in hygiene whenever changing catheter, and ensure they wash their hands before and after, avoid contamination during catheter change, and use appropriate catheters.

In those people who are at high risk of serious infection, healthcare workers will inform them to attend hospital for antibiotics or they will be prescribed antibiotics to be taken before urinary catheter change.

Abnormal urinary system

Some people have abnormalities in their urinary system, such as kidney stones or urethral narrowings, which may cause pooling of urine (when the urine stays in the bladder for longer), and could prevent the bladder from emptying properly. As a result, they are prone to repeated cystitis as bacteria is given more time in the bladder rather than being flushed out. These conditions are frequently associated with other symptoms such as severe abdominal pain and difficulty in peeing. The treatment may involve long-term antibiotics to prevent recurrence of infection.


In pregnancy, oestrogen makes the urinary passages more relaxed, leading to pooling of urine. The enlarged uterus may press on the bladder, stopping complete drainage. Pregnant women are therefore more prone to bladder infections, and UTIs are the most frequent medical complication of pregnancy.5 There may be bacteria in the urine of pregnant women and they may not experience any symptoms, and the exact reason for this is not entirely clear. But it is recommended that if bacteria is found in the urine, then pregnant women should receive antibiotics.6 This is because cystitis in pregnancy can lead to serious problems such as kidney infections and pre-term delivery.


Postmenopausal women are more likely to get cystitis. During menopause there is lack of oestrogen which makes the vaginal lining dry as less mucus is produced. Mucus plays an important role in stopping bacteria from multiplying and sticking. In addition, the urinary tract lining becomes thinner, making it more prone to damage and irritation. The evidence for taking hormone replacement therapy (HRT) to lower the risk of cystitis is conflicting, with some studies suggesting it can help prevent it and others concluding that it doesn’t.7

Inadequate bladder emptying

When the bladder does not empty fully there is pooling of urine which encourages bacterial growth. Incomplete bladder emptying may occur when taking some drugs such as antidepressants, when someone has nerve damage, and when someone is constipated.

Most mild cases of cystitis gets better without any treatment so it is reasonable to first try simple measures to help with symptoms, such as paracetamol and applying a hot water bottle over the lower abdomen for pain relief.

If symptoms do not improve within 48 hours, if you have other symptoms such as vomiting, blood in the urine, repeated cystitis, or if you are pregnant, then you should see see your GP, who will ask about your symptoms and may test your urine.
Featured image is of a person sitting cross-legged on a sofa in their pajamas
Last updated June 2019
Next update due 2022

Dr. Diana Chiu, MBChB (Hons) MRCP PGCERT (Med Ed) PhD

Diana received her medical degree, with honours, from the University of Manchester. She then went on to receive basic and specialist medical training within the north west of England. She carried out in-depth research in medicine and was awarded a PhD in 2016. Currently, she is finishing her medical training at a large teaching hospital, and one of her greatest interests is medical education. She is an advanced life support instructor and writes regularly for post-graduate examination websites, and also holds a PGCERT in medical education with distinction.

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  1. Steddon et al., Oxford handbook of nephrology and hypertension, 2nd edn, Oxford, Oxford University Press, 2014, p 707
  2. SIGN, Management of suspected bacterial urinary tract infection in adults: a national clinical guideline, [website], 2012, (accessed 1 July 2019)
  3. Jepson, G., et al., ’Cranberries for preventing urinary tract infections’, Cochrane Database of Systematic Reviews, Issue 10, 2012.
  4. Fihn, D., et al., ‘Association between use of spermicide-coated condoms and Escherichia coli urinary tract infection in young women’, American Journal of Epidemiology, vol. 144, no. 5, 1996.
  5. Al-Badr, A., and Al-Shaikh, G., Recurrent urinary tract infections management in women: a review, Sultan Qaboos University Medical Journal, August 2013, vol 13, issue 3, pp 359-367
  6. SIGN, Management of suspected bacterial urinary tract infection in adults: a national clinical guideline, [website], 2012, (accessed 1 July 2019)
  7. Raz, R., ‘Urinary tract infection in postmenopausal women’, Korean J Urol, vol. 52, no. 12, 2011, pp. 801-808.

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