Basal vs Bolus

Okay. I was diagnosed with T1 a little over a year ago. I’m definitely still learning (who isn’t?!). Something I’ve seen on this forum and on several of the blogs I enjoy reading are the words basal and bolus. What exactly do each of these mean? I was put on an insulin to carb ratio last week. Is this related at all? I’m so confused. Please help!

Thank you!

Basal is your long acting like Lantus or Levemir. Bolus is your fast acting like Humalog, Novolog or Apidra. In a pump, you use all fast acting but still have it called basal because the basal settings are dripped in at a low rate.

When you take insulin for your carb ratio, that is considered a bolus.

Thanks for explaining this so clearly! I was also diagnosed close to a year ago, and see the two terms mentioned frequently on here. My guess was right, but it’s easy to get them muddled up!

They are easy to get mixed up in the beginning!

Another way to explain it is that basal is the insulin you need all day long to keep going (your “base”) and bolus is the extra insulin you take to cover additional needs that arise, usually for a meal (a “bowl” of insulin).


bo·lus (bls)
n. pl. bo·lus·es

  1. A round mass.
  2. A single, relatively large dose of a drug that is administered for therapeutic purposes and taken orally.
  3. A concentrated mass of a pharmaceutical substance administered intravenously for therapeutic or diagnostic purposes.
  4. A soft mass of chewed food within the mouth or alimentary canal.


Thank you! I agree with Emma…definitely helps! :slight_smile:

Terry said it really well. As we live with diabetes, we tend to believe that food raises blood sugar, and insulin lowers blood sugar. That is partially right. But insulin’s real purpose it to allow the glucose to make its way from the bloodstream into the body’s cells, so your cells have energy and you can go about your day. That being said, you need insulin ALL DAY to give energy to your cells. This amount of insulin is the basal - or base. It’s why the so-called “zero carb diet” solutions to getting off insulin don’t work. The bolus, as many described, is the extra amount of insulin needed to accommodate a surge in blood glucose (from a meal, for example).

Everyone else seems to have answered your question well, but I just want to pipe in and say that I’m aware when I talk to non-diabetic how much jargon and acronyms we use. I strongly encourage you to get the book Using Insulin by John Walsh. There is an enormous amount to learn when you first are diagnosed and that is a great book to help you do it. I still refer back to it (and Pumping Insulin as well now that I’m on a pump).

I’ll have to look in to that. What type of information is in that book?