I have interstitial cystitis. Is it common to bleed after getting a bladder instillation?

Interstitial cystits. It is not common, but it is certainly possible. To some degree, it also depends on what chemical agents are being instilled. There are several different regimens for intravesical therapy. The ic bladder can also have ulcerations that are prone to irritation and bleeding in severe cases. Talk to your urologist about this.