Blood in the urine has many possible causes — from urinary tract infections and stones to diseases of the bladder, kidneys, or prostate. Visible blood in the urine should therefore be medically evaluated even if it occurs only once and is painless. Sometimes it visibly turns the urine reddish, sometimes it is only discovered in the laboratory. Even a single discoloration should be medically assessed in order to reliably determine the cause. Seeing a doctor brings clarity and is the right step to take.
Possible causes
Urinary tract infection
An inflammation of the bladder or urinary tract can cause small amounts of blood, often together with burning and frequent urination.
Urinary stones
Stones in the kidney or ureter can irritate the lining and lead to blood in the urine, often accompanied by flank pain.
Prostate in men
An enlarged prostate can cause bleeding. Even then, further evaluation is needed to rule out other causes.
Tumours of the bladder, renal pelvis or kidney
Bladder cancer and kidney cancer often first show up as visible blood in the urine — usually without pain and often only once. This is exactly why visible blood in the urine is always investigated, even if it disappears on its own. The earlier such changes are found, the better they can be treated.
Typical steps at the doctor's office
- 1First, the urine is examined more closely to narrow down the source of the blood and to detect an infection or crystals.
- 2An ultrasound examination of the kidneys and bladder provides an initial overview of the urinary tract.
- 3Depending on the result, further tests follow, such as a cystoscopy or imaging, to determine the cause with certainty.
What makes serious causes more likely
- The likelihood of a tumour-related cause increases with age; from around 45 years onward, visible blood in the urine is investigated particularly consistently.
- Smoking is the most important modifiable risk factor for bladder cancer.
- Past occupational exposure to certain dyes, paints, rubber or chemicals plays a role — even if it occurred decades ago.
- Previous bladder or kidney conditions, recurrent urinary tract infections, radiation therapy to the pelvis and certain chemotherapies also increase the risk.
What typically happens next?
Blood in the urine caused by a urinary tract infection usually clears up within a few days of treatment. After passing a urinary stone, it also subsides quickly. What matters is this: if visible blood in the urine disappears on its own, this does not replace the need for evaluation — otherwise the cause remains unidentified. If an initial examination provides no explanation, the urine is checked again over time depending on the situation.
What you can do yourself
- Note down when the discolouration occurred and whether symptoms such as burning or pain appeared as well – this helps the doctor.
- Keep in mind that beetroot, certain berries or medications can colour the urine similarly, without blood actually being present.
- Drinking enough fluids supports the urinary tract but does not replace medical evaluation.
- Do not postpone the doctor's appointment, even if the discolouration only occurred once.
Blood in the urine should always be medically evaluated, even if it occurs only once and is painless. Your general practice or urology department is the right place to go to assess the cause properly.
Frequently asked questions
- Is blood in the urine always dangerous?
- No, in many cases there is a harmless cause such as an infection behind it. However, because more serious reasons are also possible, every instance of blood in the urine is investigated.
- Do I need to see a doctor if it only occurred once?
- Yes. Even a single discoloration should be evaluated, as bleeding from the urinary tract can pause temporarily.
- Can the discoloration also come from food?
- Yes, beetroot or certain dyes can color the urine reddish. A urine test reliably distinguishes between dye and actual blood.
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