Urine
A urine test reports a dipstick reading and, when it is run, microscopy: protein, blood, glucose, leucocytes and nitrites are among the items listed. Below are the finding patterns we explain.
Value combinations explained
- Blood and Protein in the Urine Together Either finding alone has a long list behind it. Together they point at the filter itself, which is a shorter list and a faster pathway. Blood from the bladder does not bring protein with it, so the combination moves the question from the urinary tract to the kidney and from urology to nephrology.
- Blood in the Urine with No Infection Blood found on a dipstick with no sign of infection needs following up, and how urgently depends mostly on whether you could see it and how old you are. NICE sets urgent referral at 45 and over for visible blood with no infection behind it, and at 60 and over for invisible blood alongside pain on passing urine or a raised white cell count.
- Casts or Crystals Reported on Urine Microscopy Microscopy adds one thing the dipstick cannot give: it says where in the kidney something is coming from. Casts form inside the tubules, so anything caught in one was already in the kidney and was not picked up further downstream. Red cell casts are the finding that matters most — they mean the bleeding is coming from the filter itself, which needs assessment quickly. Most crystals, by contrast, mean nothing at all.
- Dark or Red Urine Color and the dipstick together split this three ways, and the split is the diagnosis. Red urine with a negative dipstick is pigment from food or a drug and needs nothing. A positive dipstick with red cells visible under the microscope is genuine bleeding. The third combination matters most: a strip reading positive while microscopy finds no cells at all. That means muscle protein or free hemoglobin, and both can injure the kidney.
- Glucose in the Urine with a Normal Blood Glucose Sugar in the urine used to mean diabetes almost by definition. It does not any more, because a widely prescribed class of diabetes drug works precisely by making the kidney dump glucose into the urine. The other explanation is a kidney that lets glucose through at a lower blood level than usual, which is inherited and harmless.
- A Raised Urine Albumin in Someone with Diabetes Albumin in the urine is the earliest detectable sign that diabetes is affecting the kidney, and it appears years before the filtration rate falls. That timing is the opportunity. Treatment started here changes the trajectory in a way that the same treatment started later cannot. But one raised result is not a diagnosis: exercise, fever, infection and a period all produce transient rises, and any of them can be the entire explanation.
- Ketones in the Urine Ketones in the urine usually mean the body has been running on fat, as it does during fasting, illness, vomiting, or a low-carbohydrate diet. On its own, with a normal glucose, that is ordinary metabolism and not a warning. The one situation that overturns this is SGLT2 inhibitor treatment, where ketoacidosis can develop with a glucose that looks close to normal — so the glucose reading cannot be used to rule it out.
- Leukocytes Positive with Nitrites Negative The nitrite square only turns positive for organisms that convert nitrate to nitrite, and several common ones do not. So a negative nitrite is weak evidence against infection, and leukocytes alone can appear with contamination, with inflammation, or with an infection the strip cannot confirm. Culture is what settles it, and whether it is worth sending depends mostly on whether you have symptoms.
- A Positive Urine Test with No Symptoms Bacteria living in the bladder without causing symptoms is called asymptomatic bacteriuria, and outside pregnancy and a few specific procedures the evidence is consistent: treating it does not help and does cause harm. That runs against instinct, which is why the finding leads to so many unnecessary antibiotic courses.
- Protein on the Dipstick with a Normal Albumin-to-Creatinine Ratio The dipstick measures how concentrated the protein is, so a dehydrated sample reads positive and a dilute one reads negative, both with the same amount of protein leaving your body each day. The ratio corrects for that by measuring protein against creatinine in the same sample. When the two disagree, the ratio is the one to believe.
- A Urine Dipstick in Pregnancy Every finding on this strip means something different in pregnancy, and one of them reverses completely. Bacteria in the urine without symptoms are usually left alone in other adults; in pregnancy they are treated, because untreated they progress to kidney infection far more often and are linked to preterm birth. Protein carries different weight too, since it is one of the features that defines pre-eclampsia.
- A Urine Test in an Older Adult Who Has Become Confused Bacteria live harmlessly in the urine of a large proportion of older adults, particularly those in care homes and anyone with a catheter, and they make the dipstick positive whether or not anything is wrong. So a positive test in someone who has become confused does not establish that infection is the reason. Treating it as though it does is the most consequential misuse of this test, because antibiotics get given while the actual cause goes unexamined.