Insulin is the medication used to manage type 1 and, in some cases, type 2 diabetes.

There are several things you should know about insulin.

  • Insulin is a hormone that lowers glucose in your blood.
  • Injected or inhaled insulin replaces what the body makes naturally. People with type 1 diabetes must take insulin to survive.
  • About half the people with type 2 diabetes will need to take insulin at some point in their lives. Taking insulin doesn’t mean you’ve failed; your body may just need extra help.
  • Insulin is safe and one of the most effective ways to lower blood glucose. It is measured in units just as milk is measured in pints and quarts.
  • Insulin is made in different strengths. Most people use a strength called U-100.
  • Insulin’s come in several different types. Some are faster-working and last for a shorter period of time while others are slower-working and last for a longer period of time.
  • Different companies make different types of insulin. Always use the same brand and type of insulin that your provider has prescribed.
  • Different injection sites (leg, stomach, etc.) may absorb some types of insulin at faster or slower rates. 
  • The main side effect of insulin is that it can cause low blood glucose levels. Knowing how to recognize and treat lows is an important part of taking insulin 

Types of Insulin

All insulin is not the same. The types of insulin differ in:

  • how fast they begin to work
  • when they work their hardest
  • how long they continue to work 
  • how is it being administered

There are two main types and functions of insulin:

  • Background Insulin (intermediate and long-acting)
  • Helps control glucose during the night and between meals
  • Take 1-2 times each day
  • Background insulins are: NPH (intermediate-acting and cloudy looking), Glargine and detemir insulin (long-acting and clear looking – also called “basal” insulin because they have no peak)
  • Mealtime Insulin (rapid and short-acting)
  • Helps control glucose after eating a meal or snack
  • Take before meals
  • You may need background insulin, mealtime insulin or both
  • Mealtime insulins are: Lispro, aspart, glulisine insulin (rapid-acting and clear looking) and Regular insulin (short-acting and clear looking)
  • Premixed Insulin
  • Premixed insulin is a combination of background and mealtime insulin.
  • Humulin 70/30 and Novolin 70/30 are premixed insulins that have some slower-acting (NPH) and some fast-acting (Regular) insulin in one bottle.
  • Humalog 75/25, Humalog 50/50 and Novolog 70/30 also contain some slower-acting insulin along with some rapid-acting (lispro and aspart) insulin in one bottle.

Your provider will tell you:

  • which brand of insulin to use
  • what type or types of insulin to use
  • how many units of each type to use
  • what time(s) to use insulin each day


Usual Action Times

Generic Name


When to take

When starts

Works best

How long it lasts

Mealtime Insulin


aspart glulisine lispro

Novolog Apidra Humalog

0-15 min before meal

10-30 min

30 min - 3 hours

3-5 hours


Regular (R)

Humulin N Novolin R

30 min before meal

30-60 min

2-5 hours

up to 12 hours

Background Insulin



Humulin N Novolin N

Does not need to be given with meal

90 min - 4 hours

4-12 hours

up to 24 hours


detemir glargine

Levemir Lantus

Does not need to be given with meal

45 min - 4 hours

minimal peak

up to 24 hours

To make an adult care appointment, call 617-309-2400 or make an appointment online.