Blood in urine after vomiting: what to know

Vomiting can leave you dehydrated, making urine darker and more concentrated, but it does not explain every episode of red or pink urine. Blood may come from a urinary tract infection, kidney stone, kidney infection, irritation, or another bladder or kidney condition. Straining during forceful vomiting can also cause small surface blood vessels to break, but blood in urine should not automatically be attributed to straining. Kidney Stones and Urinary Tract Infection can cause urinary symptoms alongside nausea or vomiting. A urine test helps distinguish blood from concentrated urine.

Contact a clinician for advice, especially if you can see blood or it happens again. Write down the timing of vomiting and urine changes, the colour of the urine, and any flank pain, burning, urgency, fever, or reduced urination. Take small, frequent sips of an oral rehydration drink or water if you can keep them down, unless you have been given fluid restrictions. Avoid taking anti-inflammatory painkillers without advice when dehydrated or vomiting. A clinician may check urine, kidney function, and the cause of vomiting.

Seek urgent care if you cannot keep fluids down, pass very little urine, feel faint, become confused, have severe side or back pain, develop fever with chills, or see clots. Go promptly if vomit contains blood or looks like coffee grounds, because that may be bleeding from the digestive tract rather than the urinary tract. Inability to pass urine is also an emergency concern.

Ask whether dehydration could explain the urine colour, how the source of blood will be confirmed, which medicines are safe while you are vomiting, and whether urine or blood tests are needed. Ask how much fluid to take and which warning signs should bring you back urgently.