Can taking an antibiotic like cefalexin affect my urinalysis?

Not directly: Most antibiotics do not alter the ua, except by killing bacteria. They can, however, alter the urine culture result. A few drugs can directly alter the ua by changing the color of the urine. Rifampin, a less-commonly used antiobiotic, and phenazopyridine/pyridium/azo, a commonly used bladder analgesic, both turn the urine a darker orange, which interferes with reading the urine analysis.