Can white blood cells or blood in the urine from a uti cause a false positive pregnancy test?

No: Home pregnancy tests are very accurate and not affected by foods, herbs, common illnesses (such as a UTI), sexually transmitted diseases, or medications. A urine test gives a reliable result 3 weeks after sex (3 weeks after when conception might have happened) or 1 week after missing a period. If done sooner, a positive result is likely real, but a negative result may be due to testing too soon.