Seeing red urine is alarming, and it's tempting to feel reassured when the colour is back to normal the next day. But the blood stopping doesn't tell you its cause, and it doesn't make an assessment unnecessary. The cause may be an infection or a stone, or it may come from the prostate, the kidneys or the bladder, and tests help tell these apart.
Does red urine always mean blood?
Some foods and medicines can change the colour of urine. A positive result for blood on a urine dipstick also needs interpreting, and usually a microscope test to confirm that red blood cells are present. Visible blood, which you can see yourself, is different from microscopic blood, which is only found on testing, but either may need follow-up depending on the circumstances.
What your doctor needs to know
When the blood appeared, whether there was pain, burning or clots, your age, whether you smoke, exposure to certain substances at work, and the medicines you take all shape the assessment. Blood thinners can make bleeding more likely, but they don't rule out a cause in the urinary tract. So the medicine shouldn't be assumed to be the whole explanation without investigation.
How the cause is found
The first steps may include a urine test, a urine culture and kidney function tests. You may also need imaging of the urinary tract and a cystoscopy, depending on your level of risk and the type of bleeding. Cystoscopy shows the lining of the bladder directly, while imaging assesses the kidneys and ureters. In some cases, signs such as protein in the urine or reduced kidney function call for a kidney specialist (nephrologist) to be involved.
When to be seen urgently
Heavy bleeding, clots that block the flow of urine, dizziness, or fever with pain in your side need urgent assessment.
Visible blood without pain needs attention too, especially if it keeps coming back or you have risk factors.
Feeling better isn't the end of follow-up
If an infection was treated and the blood was put down to it, you may be asked to repeat the urine test after treatment to confirm it has cleared. Keep your test and scan results, and tell your doctor if the bleeding returns. Finding a clear cause is far more reassuring than relying on the colour going back to normal.
This article is general health education and doesn't replace a consultation with your doctor.
