I've been on 40mg citalopram for about 20 years now. I've tried a few times to come off either tapering or cold turkey and in all cases it's been horrendous. My biggest worry is that I'll never be able to come off them as I'm on such a high dosage, even if it was tapered off over a very long period of time.
I gradually reduced the dosage from 30 to 20 mg (over the time of 3 to 4 months), then down to 10 mg (for another 2–3 months), and then I finally reduced it to 5 mg (half a 10-mg tablet) over a period of 4–6 weeks. I told my doctor beforehand, they only told me that I should fade it out slowly. But please excuse me for not knowing the exact time frames of the tapering process any more. I took my time at the beginning of the tapering and moved more quickly toward the end.
During and afterwards I didn’t notice any severe side effects, aside from the fact that the recurring emotions really overwhelmed me at times. Not only that, but I would cry at the slightest hint of emotional and romantic scenes in movies and series, which lasted for about three months. Nowadays, I feel quite normal. I miss the slight comfort Citalopram gave me, but I have my feelings back, I feel more myself again. If a bit more anxiety is the price for that, then so be it.