Can I have a suit coat adjusted....and NOT mess it up?

can it be done by a very good tailor...yes

Will it be expensive...yes

will it like come out as well as something that was the right size in the first place...no

as such, if you can exchange sizes, do so.

I agree with everything Quad said. It can be done, but it won't look as good as getting the right size to begin with and will likely be expensive to do. Try to exchange for the proper size if you can.

Congratulations on losing weight!

 

If you get it altered, you'll have to make sure that you use a tailor who pays attention to detail. If you don't, the stripes won't line up.

it's basically more work than making a coat from scratch (am i right)?

 

i got some pricing for an old black wool suit to be altered and it just wasn't worth it. 

 

i would work really hard on returning it for a smaller size.

There is a distinctive look about a suit that was clearly too big and was drastically altered to fit. It'll be "off" in a noticeable way, such that the balance of the suit will be thrown out of whack. Front pockets may migrate backward, the quarters and front will look strange, and whatever isn't taken in (shoulders, for instance) will look boxy. At best, it will look like a larger suit that has been shrunk down disproportionately.

 

I would strongly second the previous recommendations to find a new suit.

I'm not sure I agree that it can even be done. Going down four sizes is getting towards the outer limit of what alterations can do. For example, altering the pants may be impossible because at some point, the rear pockets start disappearing.

I also wonder what size suit you "really" wear. Suit sizes are chest sizes but one of the key drivers of how a suit fits is the shoulders. Re-cutting shoulders is almost never worth it. If you "really" wear a size 48 but have gone up to a 52 because you were fat, a 52 will give you a severe case of "samurai shoulder".

So yeah, what Quadcammer said. Get the size that actually fits correctly and then have it altered from there.

for the most part I agree, although I've seen some very skilled alterations tailor work some miracles. it most cases, it can be done, but the end result is a hideous mess.