Blood on a urine dipstick: what a positive result means and what happens next

A reagent strip dipped in fresh urine changes colour when it meets blood. GPnotebook explains that the chemical stick allows detection of microscopic haematuria and is very sensitive, detecting red cells in numbers as low as one to two ten-to-the-twelfth per litre, while there is no consensus on what the normal number of red blood cells should be, with recommendations varying between 2 and 5 per high-power field on microscopy.

The strip reacts to blood pigment, so it can be positive for haemoglobin or myoglobin as well as intact red cells. That is why a positive result needs confirming under the microscope.

The NHS says blood in urine is not usually anything serious but that any suspected blood needs checking, even a small amount or when you are not sure it is blood, because it must be checked out as it can be a sign of cancer, which may be easier to treat if found early. Blood can come from anywhere in the urinary tract: bladder, kidneys or urethra.

Lab Tests Online UK lists blood in the urine among the symptoms prompting urinalysis, along with tummy or back pain and painful or frequent urination, and notes that a dipstick positive for protein or blood often needs a laboratory follow-up that can take several days.

Use a clean container and a fresh mid-stream sample. Lab Tests Online UK describes cleaning the genital area first, letting the first part of the stream go into the toilet and then collecting the middle of the stream, because contamination with skin cells and bacteria can mislead the test. The first sample of the morning is the most useful because it is concentrated.

Menstrual bleeding can make a sample positive, so tell the clinician if you are on your period. Heavy exercise and some medicines can also colour the urine or affect the strip.

The NHS offers a guide: burning pain when urinating, urgency, smelly or cloudy pee and a high temperature suggest a urinary tract infection; severe pain in the side, lower back or groin that comes and goes with nausea suggests kidney stones; and in men over 50, difficulty passing urine, urgency and waking at night to pass urine suggest an enlarged prostate. It adds that you should not self-diagnose.

It may not be blood if you have eaten beetroot, are taking a new medicine that colours urine, are bleeding from the bottom, have your period, or bleed from the vagina between periods. GPnotebook notes that red cells may be present in a urinary tract infection and that patients with persistent haematuria after a UTI should be referred.

A GP may ask about symptoms, examine you, send a urine sample to the laboratory for microscopy and culture, arrange blood tests and treat infection if present. The NHS says you may be referred to a specialist for tests, which in practice often means an ultrasound scan and a look inside the bladder with a camera. If blood is still present after a urinary infection has been treated, referral is advised.

Ask for an urgent GP appointment or call NHS 111 if you see blood in your urine, which may look bright pink, red or dark brown. Call 999 if you have heavy bleeding with dizziness or cannot pass urine.