A low, or negative, urine occult blood test is normal and healthy, as it indicates that there is no blood in the urine.

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False Negative Dipstick:

- Dipsticks exposed to air
- RBCs settle out & urine not mixed
- Ascorbic acid (high concentration)
- Formaldelhyde (preservative tablets)
- High specific gravity
- Very high protein
- Urine pH <5.1
- High nitrite from UTI
- Captopril (Capoten)

In healthy individuals, fewer than 1000 red cells are excreted in the urine per minute. When 3000 to 4000 red cells are excreted per minute, 2 to 3 red cells will be seen per high power field, indicating microscopic hematuria. Gross hematuria occurs when more than 1 million red cells are excreted per minute. Hematuria can be due to lesions within the GU tract involving the kidneys, ureters, bladder, prostate, or urethra.

The most common disorders include cancer, kidney stones, renal disease, urinary tract infection, and benign prostatic hyperplasia. Transient hematuria can result from menstruation, viral illnesses, strenuous exercise, and mild trauma. Anticoagulant therapy and chemotherapy may also cause hematuria. No etiology can be determined in approximately 45% of cases of microscopic hematuria. 

A positive dipstick test for blood does not tell whether the reaction is due to red cells, red cell casts, hemoglobin casts, or myoglobin. Many conditions can lead to discrepant dipstick and microscopic findings. Any situation that causes red cell hemolysis will give a positive dipstick and negative microscopic result. Urine should be tested shortly after collection because red cell lysis may occur as the sample ages, if the pH is alkaline, or if the specific gravity is 1.010 or less. Bacterially contaminated urine specimens may contain sufficient peroxidase activity to produce a false positive reaction. False positive reactions can also be caused by vegetable peroxidase.

False Positive Dipstick:

- Myoglobin
- Oxidizing agents - bleach, detergent, iodine
- Bacterial peroxidase
- Vegetable peroxidase
- Betadine