A Banana Bag (or rally pack) is a type of intravenous fluid preparation that in addition to saline and glucose also contains other vitamins and minerals, typically thiamine, folic acid and magnesium sulfate. They are generally used for patients who are suffering from malnutrition or a chemical imbalance in the blood, particularly a lack of magnesium. They can also be beneficial to terminal cancer patients as the nutrients in the solution can help prevent muscle pain and cramps, and can also help detoxify the effect of chemotherapy on the liver and kidneys. It is also useful for severe alcoholics and those suffering from dementia.
The Banana Bag gets its name from the yellow color of the nutrient solution, and not from the fact that it's nutrient mix is similar to a banana.