Seeing blood in your urine can be alarming, and finding it on a routine test can be confusing. For many women the cause is simple and treatable, but blood in urine is a symptom that doctors always take seriously. This guide explains the types of blood in urine, its common causes, how it is investigated according to international guidelines, and which signs need urgent care.
Medically reviewed by Prof. Dr. Samir Ahmed Al-Samarrai, consultant urologist. Last reviewed: · Last updated:
Visible and microscopic blood: what is the difference?
According to NIDDK, doctors describe two types of blood in urine (haematuria). Visible blood is blood you can see. Microscopic blood does not change urine colour and is found only on testing. NIDDK notes that visible blood is less common than microscopic blood.
| Feature | Visible blood | Microscopic blood |
|---|---|---|
| What you notice | Pink, red or brown urine, sometimes clots | Nothing; urine looks normal |
| How it is found | You see it | Urine test done for another reason |
| What happens next | Always needs a medical check | Repeat test and assessment of personal risk |
Not every red colour is blood. The NHS notes beetroot and some medicines can colour urine, so a test confirms real blood. See our general guide to blood in urine.
Common causes in women
Blood can come from anywhere in the urinary tract, from the kidneys to the urethra. Common causes include:
- Urinary tract infection: often with burning, cloudy urine or fever, as the NHS describes. See urinary tract infection.
- Kidney or urinary stones: pain that comes and goes in the side, back or groin.
- Period contamination: the NHS notes that bleeding during a period can be mistaken for blood in urine, and MedlinePlus notes that blood may come from the vagina rather than the urinary tract.
- Strenuous exercise and sexual activity: listed by NIDDK as possible causes.
- Some medicines: NIDDK lists blood thinners, aspirin and some other pain relievers and certain antibiotics.
- Kidney disease: conditions that affect the kidney filters (glomeruli), such as glomerulonephritis, according to NIDDK.
- Cancer: less common, but NIDDK lists cancer of the bladder or kidney among the serious causes.
Bladder cancer and its risk factors
Bladder cancer can also cause symptoms such as stinging, needing to pee more often and repeated urine infections; these are very common and can have other causes, so recurring blood should not simply be put down to infection.
Risk factors listed by the NHS include:
- Smoking or using chewing tobacco. According to Cancer Research UK, around half of all bladder cancers in the UK are caused by smoking, and a smoker’s risk is up to 4 times that of someone who has never smoked.
- Being over the age of 60, according to the NHS.
- Past work with certain chemicals, such as in textiles or crude oil.
- A long-term urinary catheter, previous radiotherapy, or the infection schistosomiasis (bilharzia).
- A close relative who has had bladder cancer.
Why visible blood should always be checked
The NHS advises that blood in urine needs to be checked even if there is only a small amount, and MedlinePlus says you should never ignore blood you see in your urine. Blood that appears once and stops still needs assessment.
For microscopic blood, the American Urological Association (AUA) explains that the chance of finding cancer during evaluation ranges from nearly zero in people with minimal risk factors to over 6% in people with significant risk factors. Visible blood is always assessed fully, as described below. Checking early finds serious causes sooner and reassures the many women whose cause is simple.
How blood in urine is diagnosed
The doctor asks about your symptoms, smoking, work, medicines and your period. The NHS notes this may include an internal examination for women. Tests depend on your age, symptoms and risk:
- Urine tests: a urine test (urinalysis) may be repeated to confirm blood, according to NIDDK. Culture looks for infection and cytology for abnormal cells. Women who test positive during a period may be asked to repeat it, NIDDK notes.
- Blood tests: to check kidney function, blood count and clotting, as MedlinePlus describes.
- Imaging: ultrasound, CT or MRI to look at the kidneys, ureters and bladder.
- Cystoscopy: a thin tube with a camera passed into the bladder through the urethra to look at its lining. The AUA describes it as safe but somewhat invasive.
- Kidney biopsy: if kidney disease is suspected.
NICE in the UK says adults aged 45 and over with visible blood in urine that is not caused by an infection, or that continues after successful treatment of an infection, should be referred on a suspected cancer pathway, which aims for a diagnosis or ruling out of cancer within 28 days. For microscopic blood, the AUA uses a risk-based approach: fewer tests at low risk, full assessment at higher risk. If kidney filter disease is suspected, the urologist may refer you to a kidney specialist (nephrologist). See also urology for women.
Red flags and when to seek urgent care
MedlinePlus advises contacting a doctor right away, or seeking urgent care, if blood in urine comes with any of the following:
- Fever, chills, nausea or vomiting
- Pain in the side, back or abdomen
- Being unable to pass urine
- Passing blood clots
Painful or frequent urination and unexplained weight loss also need prompt assessment. The NHS advises an urgent appointment for any blood in urine, even a first or small episode.
Treatment depends on the cause
There is no single treatment for blood in urine; the doctor treats the cause once it is found. An infection may be treated with antibiotics chosen by the doctor; stones and kidney or bladder conditions each need their own plan. Repeated infections with blood may need further checks; see recurrent UTI.
Do not stop prescribed medicines, including blood thinners, on your own. Before your appointment, note when you saw the blood, your period dates and your medicines.
Frequently asked questions
Can my period cause blood in a urine test?
Yes. The NHS notes that period bleeding can be mistaken for blood in urine, and NIDDK says women who test positive during a period may be asked to repeat the test. Tell the doctor or nurse if you are on your period when you give a sample.
If the blood appeared once and then stopped, do I still need a check?
Yes. The NHS and MedlinePlus advise getting any visible blood checked, even a small amount or a single episode. Some serious causes bleed on and off, so stopping does not rule them out. Your doctor will decide which tests you need.
Is blood in urine always a sign of cancer?
No. Infections, stones, exercise and period contamination are common causes. For microscopic blood, the AUA explains that the chance of finding cancer is nearly zero in people at low risk, rising in those with risk factors such as smoking and older age. That is why assessment is based on personal risk.
Does a urinary infection explain the blood?
Often it does, and the blood should clear once the infection is treated. NICE advises that visible blood in adults aged 45 and over that continues after successful treatment of an infection should be referred for urgent specialist assessment.
Who treats blood in urine caused by kidney disease?
A urologist usually assesses blood in urine and looks for causes in the urinary tract. If the tests point to disease of the kidney filters, care is normally shared with or handed to a kidney specialist (nephrologist), who may arrange further tests such as a kidney biopsy.
Sources
- Blood in urine – NHS
- Hematuria (Blood in the Urine) – NIDDK
- Urine – bloody – MedlinePlus Medical Encyclopedia
- Quality statement 1: Suspected cancer pathway referral – NICE QS215
- American Urological Association Releases Microhematuria Guideline Amendment – AUA
- Risks and causes of bladder cancer – Cancer Research UK
- Causes of bladder cancer – NHS
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