It took about six weeks for me. Still have recurrence when it's close to my shot date but so much better.
How much time on Humira do you have now? Have you started to taper off any of your other UC meds? I'm at six weeks and have dropped the Canasa suppositories.
Late 50's male, dx'd with UC in 2003. Standard therapy is now Lialda and Canasa suppositories, prednisone for really bad flares. Green tea and cranberry extracts and saw significantly improved gas and mucus. Started Humira Sept. 2016. Now in substantial remission, thanks to the Humira and am tapering off the other meds.