References UK clinical guidance from the NHS, the British HIV Association (BHIVA), and the British Association for Sexual Health and HIV (BASHH). Last updated: April 2026.
UTIs and STIs can cause similar symptoms, especially burning when you urinate, which makes them easy to confuse. But they’re different conditions with different causes, different treatments, and different implications. A UTI is a bacterial infection of the urinary tract, usually caused by gut bacteria. An STI is an infection transmitted through sexual contact.
The overlap in symptoms is the main source of confusion. Both can cause pain when urinating, frequent urination, and discomfort in the lower abdomen. But the treatments are different, and misdiagnosing one as the other means you won’t get better. Here’s how to tell them apart.
Not sure which one you have? Get a home STI test kit
UTI vs STI: Key Differences
| Feature | UTI | STI |
|---|---|---|
| Cause | Bacteria (usually E. coli) from the bowel entering the urethra | Bacteria, viruses, or parasites transmitted through sexual contact |
| Sexually transmitted? | No (though sex can trigger UTIs by pushing bacteria into the urethra) | Yes |
| Burning when urinating | Yes (common) | Yes (chlamydia, gonorrhoea, herpes) |
| Frequent urination | Yes (common) | Less common |
| Cloudy or smelly urine | Yes (common) | Uncommon |
| Unusual discharge | Uncommon | Yes (chlamydia, gonorrhoea, trichomoniasis) |
| Blood in urine | Possible | Less common |
| Sores, blisters, or warts | No | Yes (herpes, syphilis, HPV) |
| Lower abdominal pain | Yes (bladder area) | Yes (especially PID from chlamydia/gonorrhoea) |
| Fever | Yes (if kidney infection) | Uncommon (except HIV seroconversion) |
| Treatment | Short course of antibiotics (trimethoprim, nitrofurantoin) | Specific antibiotics or antivirals depending on the STI |
Symptoms That Point to a UTI
- Strong, persistent urge to urinate
- Passing small amounts of urine frequently
- Cloudy, dark, or strong-smelling urine
- Burning or stinging sensation when urinating
- Pressure or cramping in the lower abdomen or back
- Blood in the urine (pink, red, or cola-coloured)
- Feeling generally unwell, especially with fever (suggests the infection has reached the kidneys)
UTIs are much more common in women than men. Around 50% of women will have at least one UTI in their lifetime. They’re not sexually transmitted, but sex can trigger them.
Symptoms That Point to an STI
- Unusual discharge from the vagina or penis (the strongest distinguishing symptom)
- Burning when urinating AND discharge together
- Sores, blisters, or warts on the genitals
- Bleeding between periods or after sex (women)
- Pain during sex
- Itching or irritation in the genital area
- Swollen lymph nodes in the groin
The key differentiator: discharge. UTIs rarely cause genital discharge. If you have burning when urinating AND unusual discharge, an STI is more likely than a UTI.
Can You Have Both at the Same Time?
Yes. It’s possible to have a UTI and an STI simultaneously. In fact, some STIs can increase your risk of developing a UTI because genital inflammation makes it easier for bacteria to enter the urinary tract.
If you’ve been treated for a UTI but your symptoms haven’t fully resolved, or if you have discharge alongside urinary symptoms, get tested for STIs. Standard UTI treatment (trimethoprim or nitrofurantoin) does not treat chlamydia, gonorrhoea, or any other STI.
Can Sex Cause a UTI?
Sex doesn’t cause UTIs directly, but it can trigger them. During sex, bacteria from the genital and anal area can be pushed into the urethra. This is why UTIs are sometimes called “honeymoon cystitis.”
Tips to reduce sex-related UTIs:
- Urinate within 30 minutes after sex (flushes bacteria from the urethra)
- Stay hydrated
- Wipe front to back
- Avoid using spermicides, which can irritate the urethra
How to Get the Right Diagnosis
- For UTI: A urine dipstick test (available at your GP or pharmacy) can detect signs of infection. A urine culture identifies the specific bacteria.
- For STI: A urine sample or swab tested specifically for chlamydia, gonorrhoea, and other STIs using NAAT testing. Standard UTI tests do NOT screen for STIs.
If you’re unsure, the safest approach is to test for both. Many sexual health clinics and home test kits can screen for UTI and STIs from the same urine sample (processed differently).
Order a home STI test or visit your nearest sexual health clinic.
Read more: What is chlamydia? | What is BV? | Pain when urinating — STI or UTI?
Frequently Asked Questions
Can chlamydia be mistaken for a UTI?
Yes. Both cause burning when urinating and lower abdominal discomfort. The key difference is discharge: chlamydia commonly causes unusual discharge, while UTIs usually don’t. If UTI treatment doesn’t resolve your symptoms, get tested for chlamydia.
Will UTI antibiotics treat an STI?
No. Trimethoprim and nitrofurantoin (standard UTI antibiotics) do not treat chlamydia, gonorrhoea, or any other STI. You need specific antibiotics for each infection.
Can a man get a UTI from sex?
UTIs in men are uncommon but can happen. A man with burning and frequent urination after sex is more likely to have an STI (chlamydia or gonorrhoea) than a UTI. Men with these symptoms should get an STI test before assuming it’s a UTI.
I keep getting UTIs after sex. Should I get tested for STIs?
If UTI treatment resolves your symptoms each time, recurring UTIs triggered by sex are a common pattern and don’t necessarily indicate an STI. However, if symptoms persist despite UTI treatment, or if you develop discharge, getting an STI test is sensible.
Related reading
- A to Z of Sex: Sexual Health Terms Explained
- Alcohol and HIV: What You Need to Know
- Anxiety and HIV: Coping and Getting Support
- Are All STIs Curable?
- Blood Problems and HIV: Anaemia, Low Platelets and More
Sources
- NHS — Sexual health conditions
- BASHH — UK clinical guidelines for STI management
- British HIV Association (BHIVA) — HIV treatment guidelines
- Terrence Higgins Trust — sexual health information
- UK Health Security Agency — STI surveillance data
Steve Page is a recognised expert on Sexually Transmitted Diseases (STDs) and STD treatments, having published numerous articles in peer-reviewed journals and presented his research at conferences around the world. He has an in-depth understanding of the latest medical research on STDs, and is an advocate for the development of new treatments and protocols to improve the health of those affected. In addition to his research, he has dedicated his career to understanding the causes and symptoms of STDs, as well as how to best treat those impacted.
