Depends on how you use your insullin. My doctor gave me an insulin
to carbohydrate ratio to use. I use 1 unit of insulin
to every 12 grams of carbs I eat. The less carbs I eat, the less insulin
I use. I have a very physical job for four hours a day and I don't even need my Humalog when I eat lunch. My pen generally lasts me the whole month. My Humalog is only good for 28 - 30 days.