From the Research
Laxatives that can cause urine color changes include senna-containing laxatives, cascara sagrada, and phenolphthalein, which can turn urine reddish-yellow to brown, yellowish-brown, or pink due to the presence of anthraquinone derivatives 1. These color changes occur because the stimulant laxatives are partially absorbed into the bloodstream and then excreted by the kidneys, altering urine appearance. The color change is more pronounced in alkaline urine.
- Senna-containing laxatives (such as Senokot) commonly turn urine reddish-yellow to brown.
- Cascara sagrada may produce a similar effect, causing yellowish-brown or pink discoloration.
- Phenolphthalein, once common in laxatives but now less frequently used, can cause pink or reddish urine. It's essential to distinguish these benign color changes from hematuria (blood in urine), which requires medical evaluation. If you experience urine color changes while taking laxatives, it's typically not cause for concern, but persistent or unexplained changes should be discussed with a healthcare provider. The most recent and highest quality study on laxatives does not specifically address urine color changes, but it provides information on the safety and efficacy of laxatives, including senna and polyethylene glycol (PEG) 2, 3. However, a study on the detection of laxatives in urine mentions that anthraquinone laxatives, such as senna, can be detected in urine using high-performance thin-layer chromatography 1. Another study reports a case of metronidazole-induced urine discoloration, but this is not directly related to laxatives 4. In summary, while the exact mechanism of urine color changes caused by laxatives is not fully understood, it is clear that certain laxatives, such as senna and cascara sagrada, can cause changes in urine color due to the presence of anthraquinone derivatives.