It's a really interesting question, and lots of people here have asked the same question, with loads of different replies as well. I wonder why so many of us would like an answer to this question? My theory is that we hate to "bother" our doctor (don't want to waste his/her time, worried about cost, concerned about "crying wolf", don't want to be seen as being too pushy, etc etc) so we just want to know at what point we should be concerned enough to pester for further / different treatment.
There is a tool called SCCAI (Simple Clinical Colitis Activity Index), which offers a scoring system for your symptoms, depending on severity. The index leaves out pain, though. I'm very lucky in that I don't have intense pain very often at all, but I know a lot of the people here have a terrible time just with the pain. Also, I've seen the remission point defined as "less than 2.5" using this system as well as "less than 5". Apparently, though, it does correlate very well to earlier (and very complicated) measuring/scoring techniques, and does have the advantage that you don't need to know the outcome of blood tests etc to use it. It's also mainly objective, which is what I like.
Personally, I'd say remission:
No (or very little) pain. No blood, up to 3 formed bowel movements per day, not having to dash to the loo when the urge comes, and not being woken in the night by the need to go. Oh, and not feeling so darn tired all the time.
Ideally, I'd like to reach "pre-illness" stage, but wouldn't have a problem living with an extra couple of bms a day, so long as it's not "Oh my god, am I gonna make it to the loo in time? What if it's busy? What if the buckle on my belt catches again?"
UC - diagnosed Sep 2008 - awaiting colonoscopy to determine extent
Omeprazole 2 x 20mg
Calcium (Adcal-D3) 1500mg
Mesalazine 8 x 500mg
Mesalazine foam enema
Multivitamins x 2