When drinking ensure you should drink at least 1 to 2 servings of ensure per day for the most benefits from it.
However it's not recommended to drink more than 3 servings everyday of ensure because it could be unhealthy for some people.
At 3 servings the level will not exceed the Upper Tolerable Intake Levels of Vitamins and Minerals.
2 to 3 servings of ensure should provide you with enough nutrition and if it's not then you have health issues that need resolved by a doctor.
If you're underweight and need to gain weight then drinking at least 3 bottles of ensure per day should help you put on the needed weight.
Ensure is a easy to serve or drink nutrition supplement and if you have nutrition issues or can't gain weight properly then drinking ensure can help you improve your health and nutrition and help you put on the weight.