I have low iron and vitamin d. I need to gain some weight fast. I also have IBS and night sweats every night....so should I drink ensure or boost everyday to put some ponds on (like maybe 15 to 20 pounds within a month)?

Calories. Ensure and boost are good sources of extra calories, but ou must also eat plenty of good quality food on a balanced diet. Sounds like you're already seeing a doctor about your problem and they have sent lab tests. Green leafy vegetables have lots of iron. Ask your doctor for advice, or consult with dietician. Hope this helps!