How many calories should be in your protein powder?

My dietician told me to find a protein powder before surgery so I got Six Star unflavored whey protein powder. It has 20 grams of protein per scoop which is what she wanted me to have, but it also is 120 calories for one scoop. Is this too much, or is this right on the money?

Does anyone use this brand of protein powder? 

Thank you!

I haven't heard of that brand, but the two brands I use have about 100 kcal per scoop (20-23 g of protein, depending on the brand), so the 120 kcal per scoop in Six Star isn't far off the mark.

Thank you so much!

Premier Protein has 30g and 160 calories.  Plus, my nutritionist asked me to start using milk instead of water which adds 80-100 calories to the muscle milk I sometimes use.  It sounds like you're doing fine.

My dietician told me...

Things to remember when picking out an appropriate protein shake:
Nutrition per serving:

I was given the following rule of thumb: 10% of the number of calories should be equal or more than the protein gr.   another words 190 calories should give you 19 grams or more.

energy first is a great protein powder, it has 37 grams of protein and only 90 calories per scoop.  It's a real soft, fine powder which mixes very well and it taste great.   www.energyfirst.com

What about the number of carbs per serving?  Mine has 15 carbohydrates per serving and I am not sure if that's too high...