I've been on these medications for several years and never experienced any side effects. I'm not sick any more than normal. I've found remission, the only time it's ever occurred since I got uc. Quality of life is the biggest concern when managing chronic illness, you shouldn't let fear hold you back, and make your suffering from uc symptoms longer than is necessary.
Yes, they do have serious side effects and we're all a little concerned when first considering these medications. What helped me greatly was weighing the actual risk versus benefits which is a key point to consider when starting a new class of medications. There are roughly mid-60-ish percent odds that immunomodulators or the same that biologics will improve your uc symptoms. Side effects are statistically small, few experience them and they're serious when they do occur.
The most concerning side effect of these medications is lymphoma which has odds of 6 in 10,000 (or 0.06 percent) compared to 2 in 10,000 ( or 0.02 percent) for the general population. Of those who get it, 66 percent successfully put theirs in remission. To put those odds into perspective, the odds of death due to heart troubles is 1 in 5, and from a car crash in the usa are 1 in 133.
The second concerning area is increased risk of infections. We're talking about
the type of infections that typically require antibiotics to treat (uti, bronchitis, sinus, etc.). You should seek treatment earlier if you suspect you're coming down with one, rather than wait it out, because the symptoms will start sooner and become more severe with a slightly reduced immune system. Normal cuts bruises and scrapes are fine, no worries.
The Crohn's and Colitis Foundation of America is the source for these statistics:
Usually immunomodulators (Imuran, 6mp, or aza) are tried before biologics (humira, remicade, simponi, entyvio. However, some gastroenterologists jump straight to biologics as they're much quicker working.