Due to the presence of pigmented substances such as urochrome, urochrome and urobilinogen, normal human urine is a pale yellow transparent liquid. In addition, the color of urine is influenced by various factors such as diet, medication, exercise and disease. Abnormal color of urine, especially red color with urinary tract irritation, is often an alarm signal of disease. However, it is important not to assume that red urine is the result of disease at first sight, as it may be the result of certain medications. Some of the drugs that may cause red urine are summarized to alert medication users. Rifamycin This class of drugs includes rifampicin, rifaximin and rifapentine. The metabolites have pigmented groups and are excreted in a wide range of ways, so they can cause various secretions such as tears, saliva, nasal secretions, sweat and urine to be red in varying degrees. Nitroimidazoles This class of drugs includes metronidazole, tinidazole and ornidazole, the metabolites of which can make the urine dark red. Anthracycline antineoplastic drugs This group of drugs includes adriamycin, epirubicin, erythromycin and idarubicin, which can cause red staining of urine within 1 to 2 days after administration, and usually disappear after 2 days. Pigmented substances Some plant or mineral-based herbal medicines contain natural pigments, which are not absorbed by the body when ingested in large amounts and are excreted in the urine. Others such as senna, rhubarb, and vitamin B2 (riboflavin) can also make the urine dark yellow or even brown. Warfarin The urine may be red to orange during administration in alkaline urine; the color may disappear when acidifying the urine to a pH less than 4. Hydroxocobalamin is a dark red compound, which is a precursor of vitamin B12. It is made by replacing the cyanide group of vitamin B12 with hydroxyl group, and can combine with cyanide ion to form cyanocobalamin in the body to detoxify cyanide. Hydroxocobalamin can cause red staining of skin, urine and other body fluids. Imipenem Cilastatin Changes in urine color can be seen, especially in children with the drug can appear non-blood red urine, which is caused by drug coloring and should not be confused with hematuria. Levodopa 80% of this drug is degraded to dopamine metabolites within 24 hours after oral administration, mainly homovanillic acid and dihydroxyphenylacetic acid, which are excreted by the kidneys, and the metabolites can turn the urine red, or possibly black or brown. Salazosulfapyridine may cause the urine to be orange in color. Mesalazine This product is used in the treatment of ulcerative colitis. It is metabolized to N-acetyl-5-aminosalicylic acid and excreted by the urine, which is colorless, but may become reddish-brown when combined with hypochlorite containing detergents. Methyldopa is used in the treatment of hypertension and is excreted mainly in its original form via the kidneys, but can also be combined with hypochlorite-containing detergents to appear brown or even reddish-brown. Epalrestat This product is used for the treatment of diabetic neuropathy and may appear maroon in the urine after administration. The red color of urine caused by the use of the above drugs is a normal reaction caused by the drugs and needs to be distinguished from hematuria. In addition, clinical attention should still be paid to hematuria caused by urotoxic drugs, such as non-steroidal drugs, aminoglycosides, vancomycin, cyclophosphamide, etc., which are more toxic to the urinary tract and can also clinically manifest as red hematuria when used, and once similar symptoms occur, prompt medical attention should be sought.