Depends on a few factors, such as how long have they been tweaking (on speed).

If they did something like snort a line, they most likely would only be a little hungry and a lot tired and sleep a 'normal' shift of 8-9 hours.

If however they had been tweaking for a few days, they would be exhausted, super depressed and end up 'crashing' (passing out) for a day, possibly longer, wake up shaky (low sugar) and very, very hungry.

I used to do crystal meth on a regular basis (weekends, vacations, etc). The right way to do it (yeah I know doing meth ain't right) but the right way to do it is to hydrate BEFORE one doses with something like Gatorade, eat a decent meal 2 hours BEFORE getting high...

I would also only tweak Friday night and early Saturday, giving myself Saturday night and half of Sunday to rest, eat, take it easy and by Monday I was ready to face the job.

Now here is the kicker - most tweakers (meth users) actually know how to do it properly and are 'weekend warriors' - that whole faces of meth is about the worst case individuals. This is sort of like pointing at all the alcoholics who lost everything living on the street and saying this is where alcohol is going to put you.

Loosing teeth? I'm 48 years old and used meth since I was 22 years old on and off. Aside from having an impacted wisdom tooth removed in my 30's, I have all of my teeth. Picking? Never happened. A lot of professionals are on speed/meth and you would never guess it...

So the idea that one is going to end up in dire straights because one is using meth is off.

And not everyone gets bat shit crazy while tweaking... Sure they may talk a little more, work a little harder, but they ain't all over the place doing insane shit.

If you are sitting here asking 'what are the signs of coming down' chances are pretty high you are not dealing with an off the wall tweaker... Their mood would definitely drop within an hour, going from manic to depressed, and they would have to go lay down and sleep...

So if there is a tweaker in your life, they most likely are the weekend warrior type, which in this case its going to be real hard to know when they are coming down since it won't be after a week long session of tweaking hard or something.