Urine protein is detected when urine is clouded by acidification and heating. Normal people generally excrete 40-80 mg of protein per day in their urine, with an upper limit of 150 mg, called physiological proteinuria. Due to the small amount, a routine laboratory test is negative, and more than 150 mg/day is considered abnormal proteinuria. The amount of urinary protein excretion can increase during strenuous exercise, heavy physical labor, emotional excitement, excessive cold, excessive heat and stress, which is called transient proteinuria and can return to normal after a few hours or days.