Yes, interstitial cystitis (IC) can cause blood in urine. In a study of 148 IC patients followed over 18 months, 41% had at least one episode of hematuria, and broader estimates suggest up to 30% of IC patients experience it at any given time. The bleeding can be microscopic (only detectable on a lab test) or visible to the naked eye, depending on the type and severity of bladder inflammation involved.
That said, blood in urine is not a hallmark symptom of IC the way pain, urgency, and frequency are. Its presence actually raises a diagnostic flag that other conditions need to be ruled out, which makes understanding the connection between IC and hematuria especially important.
Why IC Causes Bleeding
The bleeding in IC comes from damage to the bladder wall itself. There are two main ways this happens, and they correspond to the two recognized subtypes of the condition.
The first involves Hunner’s lesions, which are inflamed patches on the bladder lining where small blood vessels radiate toward a central scar. In these areas, the protective surface layer of the bladder can be partially or completely stripped away. One study found that in more than half of bladder tissue samples taken from Hunner’s lesions, moderate to severe loss of the surface lining was present. When that lining erodes, the fragile tissue underneath is exposed to urine, leading to inflammation, irritation, and bleeding. This type of IC tends to produce more noticeable bleeding.
The second involves what doctors call glomerulations: tiny pinpoint hemorrhages scattered across the bladder wall. These appear in IC patients who don’t have Hunner’s lesions, which is the majority. Glomerulations are typically only visible during a procedure called hydrodistention, where the bladder is filled with fluid and examined with a camera. The bleeding pattern looks like dozens of small red dots spread across at least three-quarters of the bladder surface. In everyday life, this type of damage is more likely to show up as trace blood on a urinalysis rather than something you’d notice in the toilet.
What the Bleeding Looks Like
Most IC-related bleeding is microscopic. You won’t see a color change in your urine, but a urine test will pick up red blood cells. This is often discovered incidentally during routine testing or when a doctor is working up your IC symptoms.
Visible blood is less common but does happen, particularly during flares or in patients with Hunner’s lesions. It may appear as pink, red, or tea-colored urine. The amount can vary from one episode to the next, and some patients go months or years between episodes while others notice it more regularly. During the 18-month follow-up study mentioned above, the 41% of patients with hematuria didn’t all have it continuously. Many had isolated episodes that came and went.
Why Blood in Urine Needs Extra Attention
Here’s the critical point: blood in urine is actually more strongly associated with other bladder conditions than with IC. In bladder cancer, hematuria is the primary symptom in 63% to 100% of cases. IC, by contrast, is more defined by pain during bladder filling, urinary urgency, and frequency that persists at night. The absence of hematuria has historically made a diagnosis of IC more likely, not less.
Because IC is diagnosed by excluding other conditions, any new or unexplained blood in your urine requires investigation even if you already carry an IC diagnosis. The American Urological Association guidelines recommend that basic IC evaluation include a urinalysis and urine culture. If you have a history of smoking or unexplained microscopic blood in your urine, urine cytology (a test that checks for abnormal cells) may also be appropriate given the elevated risk of bladder cancer.
Urinary tract infections are the other major cause of bloody urine that needs to be separated from IC. Both conditions can cause urgency and discomfort, but UTIs produce positive urine cultures while IC cultures come back negative. This distinction matters because IC symptoms can mask a UTI, and a UTI can trigger an IC flare, making the two easy to confuse.
When Bleeding Signals Something More Urgent
Occasional trace blood in your urine during an IC flare, while worth mentioning to your doctor, is a known feature of the condition. Certain situations call for faster action:
- Visible blood that appears suddenly or worsens, especially if it’s a new symptom or noticeably heavier than previous episodes.
- Blood clots in your urine, which can indicate hemorrhagic cystitis, a more severe form of bladder inflammation.
- Difficulty passing urine, which can happen if clots are large enough to partially block the flow.
- Blood accompanied by fever, flank pain, or weight loss, symptoms that point away from IC and toward infection, kidney problems, or malignancy.
If you’ve been living with IC and have always had clean urinalyses, a new finding of blood warrants a fresh evaluation rather than an assumption that your IC has simply gotten worse.
Managing IC-Related Bleeding
There’s no separate treatment specifically for IC-related hematuria. The bleeding is a byproduct of bladder wall inflammation and damage, so managing it means managing the underlying IC. When inflammation decreases, bleeding typically decreases with it.
For patients with Hunner’s lesions, which tend to produce more significant bleeding, treatment often targets the lesions directly. Procedures to remove or cauterize the inflamed patches can reduce both pain and bleeding. For the more common non-Hunner’s type, treatments focused on calming bladder inflammation and protecting the bladder lining are the standard approach.
Staying well-hydrated dilutes your urine and can reduce irritation to an already compromised bladder wall. Avoiding known dietary triggers (acidic foods, caffeine, alcohol, and spicy foods are common culprits for many IC patients) may help reduce the frequency and intensity of flares, which in turn can reduce episodes of bleeding. Tracking whether blood in your urine correlates with specific foods, stress, or menstrual cycles can give you and your doctor useful information about your individual pattern.