What could cause high luckyotes but negative nitrates. could a yeast infection cause those test results or is it still likely to be a uti?

Maybe UTI: I assume you’re talking about a urinalysis. Leukocytes in the urine = pus in the urine. Usually (but not always) caused by a UTI. Nitrites in the urine are produced by a specific type of bacteria (Enterobacteriacae). If you have infection caused by a different type of bacteria, leukocytes will be (+), nitrites (-). See your doc (he/she may not know this)😜