I don't know how far you can recover without intervention. I suppose it depends how dehydrated you really are.
I got a new loop ileo on 9/1 and ever since I have been battling dehydration constantly. When I saw my GI last week he gave me a recipe for an oral rehydration solution. I finally made a batch up on Friday and holy cow could I feel the difference within a few hours of drinking two glasses. I went from fatigued and nearly passing out every time I stood up to feeling almost normal.
He told me where to buy polycose powder in our city; one particular pharmacy always carries it. It may be hard to find, I don't know. It's in a short can like you'd see of baby formula. It was in the same section as the Pedialyte.
I'll warn you, this stuff tastes terribly salty. It really does work wonders though. I add a packet of Splenda to a glass and it makes it slightly less repulsive.
Because I'm on Zestril for borderline high blood pressure and also diabetic, I need to have bloodwork done to check my potassium checked due to the No Salt.
Oral Rehydration Solution:
4.5 Tbsp Polycose Powder
9/10 tsp Table Salt
3/4 tsp Baking Soda
1/2 tsp "No Salt" (potassium chloride)
Diet Kool-Aid (with aspartame, envelope says it makes 1.5L) (my packets say they make 2L)
Mix all ingredients well with 1500mL (6 cups) water and chill.
Alternate Oral Rehydration Solution:
1 Litre Pedialyte Solution
1/3 tsp Table Salt