Back in the days of Regular insulin, taking injections at least 30 minutes before a meal was important because it took quite a while for the insulin start working. Nowadays most people use rapid-acting insulin (Humalog, Novolog, or Apidra), which we think of as starting to work in 10 to 15 minutes. But how many people actually take it 10 to 15 minutes before eating? When we first had rapid-acting insulin available one of its claims to fame was that it started working rapidly and we could take it right before the first bite of a meal, or even right after eating.
What we know now is that taking rapid-acting insulin 10 to 15 minutes prior to eating really can lower the A1C. Of course, that requires some planning and knowing how much we’re going to eat. It still makes sense to wait when someone who does not know what or how much they are going to eat, or when eating away from home. It’s always safer to know the food is ready and available before injecting rapid-acting insulin.
Some guidelines for when to take rapid-acting insulin are as follows: if the blood glucose is below 100 take insulin right before eating a meal, if the blood glucose level is in the 100s wait ten minutes, and if the blood glucose is in the 200s wait 20 minutes.
As far as long-acting insulin goes, Lantus can be given any time during the day/evening as long as it is consistent from day to day. For those who take Lantus or Levemir twice a day, taking it consistently about 12 hours apart is a good plan, although personally I take Lantus at 7 am and 10 pm and that works well for me. The point is to be consistent so your background insulin coverage is consistent. I once worked with a teen-ager who could only remember to take her Lantus if she took it at noon – and that’s fine!