What Are The Side Effects Of Ensure High Protein Shake?

Hi ... I drank an Ensure High Protein Shake tonight and got very dizzy. Can you tell me if this is normal? I am 71 and am 5 6 and weigh 156. I have been on a 1000 calorie a day diet for 4 weeks now and have lost 9 lbs. I drink a lot of water and no alcohol. I am getting 50 Grams protein daily and take vitamins. Could it be that I got a rush from the Ensure? I have never had it before tonight.