According to Pet Education, healthy rabbits can have red urine because they have ingested a plant-heavy diet, especially if the plants contain beta-carotene. Antibiotics also cause some rabbits to excrete red urine, and dehydration and stress cause reddish discoloration of urine to occur.
In some cases, rabbit urine is red because it contains blood, a condition known as hematuria. This is a symptom of urinary tract disease, which can include polyps, kidney or bladder stones, cancer or infection. Rarely, rabbits may have red urine as a symptom of advanced liver disease. A rabbit that has red urine lasting longer than a few days requires veterinary attention.