What is the ruling on taking subcutaneous chemical injections during fasting to treat the resulting fatigue and pain, given that the work requires presence for 24 hours?

Medical injections in Ramadan are of two types: nutritional, and these are not permissible for a fasting person to use except out of necessity. They invalidate the fast, and that day must be made up. Non-nutritional (purely medicinal), and these are permissible because they are not in the meaning of food.