Haematuria is the presence of red blood cells in the urine. The presence of 10 or more RBCs per high-power field is abnormal. Urinary dipsticks are very sensitive and can be positive at <5 RBCs per high-power field. Red or brown urine does not always indicate haematuria (haemoglobinuria, myoglobinuria, medication, and food).

Urate crystals are commonly present in the urine of newborn babies. They can produce a red discolouration of the nappy ("brick dust" appearance) which is sometimes mistaken for blood. Blood in the urine may come from sources other than the urinary tract (eg vaginal haemorrhage, rectal fissure). Common causes for microhaematuria include in association with viral infections, UTI, Trauma, HSP. If you find microscopic haematuria in the setting of an acute febrile illness, exclude UTI by urine culture and arrange for the urine to be tested again after the acute illness has passed.