Had urinalysis last week. showed 3+ for urine in blood. no uti. ph, leukocyte, nitrite, protein, glucose, urobilinogen, bilirubin, hemoglobin all negative. bun was 10 (5-18). creatin .72 (.60-1).what could cause this if it was not menstruation blood?

So many things I cannot start to answer here. If it was not a clean catch urine sample I would repeat especially if you were having your period. Clean catch means you clean yourself with wipes and then start peeing and insert collection cup into to stream and collect your urine sample. Now you will know if blood from urine system rather than elsewhere.

3+ blood by urinalysis means 3+ hemoglobin so your statement was inaccurate. If you truly has blood in the urine, microscopic exam will show more 5 RBCs/hpf and this is true microscopic hematuria. There are a lot of urinary tract conditions which can cause hematuria such as cancer, stone, kidney disease, etc. You will need to see at least a urologist if you truly have microscopic hematuria.