Blood in urine: what a positive urine test means and what comes next

Blood in urine, on a urine test, usually means the test strip reacted to haemoglobin, the protein that carries oxygen inside red blood cells. Most of the time the amount is far too small to see. The NHS describes blood in urine as not usually serious, but always worth having checked. A positive result is a reason for a closer look, read alongside a microscope count of red cells and the rest of the urinalysis.

What the test measures

The blood pad on a urine dipstick detects the peroxidase activity of haemoglobin. Whole red cells set it off, but so does free haemoglobin released when red cells break apart, and so does myoglobin, a similar protein that comes from muscle. A positive pad says that something carrying haem is in the urine. It does not prove that intact red cells are there.

That is why the strip is paired with microscopy. A spun-down sample is examined and red cells are counted per high-power field (HPF), the area seen at 400 times magnification. Blood that colours the urine is visible, or gross, haematuria. Blood found by testing alone is microscopic haematuria, and it usually causes no symptoms.

Normal range

Healthy urine usually contains no detectable haemoglobin. The strip is sensitive: it picks up more than 90% of samples with haematuria, and a weak positive can appear at red cell levels that are physiological. Microscopy settles the question.

Result	Where it comes from	How it is usually read
Blood negative	Dipstick	No haem detected, the usual finding
Blood trace or positive	Dipstick	Haem detected, to be confirmed or ruled out under the microscope
Fewer than 3 red cells per HPF	Microscopy	Within the usual range for adults
3 or more red cells per HPF	Microscopy	Microscopic haematuria, as the American Urological Association defines it for adults

Definitions differ a little. The American Urological Association counts a single, properly collected sample; some other guidelines want the finding in two of three samples, and in children the usual threshold is more than 5 per HPF. Automated analysers may report red cells per microlitre (µL) instead. Ranges vary by laboratory and method, so read your result against the range on your own report.

Microscopic blood is common. A 2018 review put its frequency in routine practice at about 4 to 5 in every 100 people tested.

What a positive result usually points to

Most causes sit in the urinary tract itself: an infection of the bladder, kidney, prostate or urethra, kidney or bladder stones, an enlarged prostate in older men, a recent procedure on the urinary tract, vigorous exercise, or sexual activity. Blood from a period, from the vagina or from the back passage can also end up in the sample without coming from the urinary tract at all.

Less often, the blood comes from the kidney's filters, the glomeruli, as in IgA nephropathy, or reflects a blood-clotting disorder or sickle cell disease. Cancers of the bladder, kidney or prostate are among the causes doctors rule out, which is why unexplained blood is followed up rather than left. Most follow-ups find something simpler: in one review, about 80% of people with microscopic blood that did not come from the glomeruli, and who had no symptoms, had no cause of clinical significance.

What a doctor typically looks at next:

• A repeat urine test with microscopy, once any passing cause such as an infection or a period has settled.
• A urine culture, if an infection is suspected.
• Protein in the urine, kidney function in the blood, and blood pressure. Protein, red cell casts and misshapen (dysmorphic) red cells point towards the glomeruli. Their absence points lower down, to the bladder, prostate or urinary tubes.
• Personal risk: age, sex, smoking, how much blood there is, whether it persists and any past visible blood. This shapes whether imaging or a look inside the bladder (cystoscopy) is offered, a decision the guideline asks doctors to share with the patient.

What a negative result means

A negative strip is the usual finding. High doses of vitamin C can turn a true positive negative, and very concentrated urine can hide blood on the strip, so if you have symptoms the result is read with them, not instead of them.

What moves it

• Exercise. Exercise-related blood in the urine is fairly common, especially after long-distance running, and a repeat test 48 to 72 hours later is expected to be clear.
• Periods. Menstrual blood can get into the sample, so a positive result taken during a period is usually repeated afterwards.
• Medicines. Blood thinners, some antibiotics, aspirin and other pain relievers are linked with blood in the urine.
• Muscle or red cell breakdown. Myoglobin from muscle damage, or haemoglobin from red cells broken down in the bloodstream, turns the strip positive with few or no red cells seen.
• Colour without blood. Beetroot, blackberries, rhubarb and some medicines can turn urine pink or red with no blood in it.
• Time and handling. A sample should be examined within two hours or kept cold. In a 2026 study of stored urine, red cell counts became unreliable within 4 to 8 hours while the strip's blood reading held for at least 8, so the two results do not always match.

Preparing for the test

A urine test needs no fasting. If blood tests that do need fasting are taken at the same visit, follow the instructions for those. The sample is usually a midstream "clean catch": wash your hands, clean the genital area, pass a little urine into the toilet, then collect the middle of the stream.

Tell the person taking the sample if you have your period or bleeding haemorrhoids, if you exercised hard in the previous two or three days, and about every medicine and supplement you take, including vitamin C. Do not stop any medicine before a test unless your doctor tells you to.

How Clare's panel handles it

Clare's panel includes a urinalysis, and in it Urine Blood / Hemoglobin is measured by the lab. The same sample also gives Urine RBC, the red cell count under the microscope, so the two can be read together.

Related tests

Blood in urine is read with Urine RBC, which shows whether intact red cells are present, and Urine Protein, which helps separate a kidney-filter cause from one lower down. Creatinine and Estimated GFR (eGFR) show how well the kidneys filter. For what the blood side of a full panel involves, see Comprehensive blood test in Dubai: what to expect.

Why the result means more over time

One positive strip is a snapshot. Doctors usually recheck it on a fresh sample; a result that clears once a period, an infection or a hard week of training has passed usually had a passing cause. Blood that keeps showing up is the pattern that leads to further tests, and how often to recheck after a clear work-up is set with your doctor, as guidance differs. When Clare opens, each urine result will sit in one health account next to the ones before it, so a one-off and a repeat are easy to tell apart.

Clare is opening with a waitlist at clare.health.