Rapid acting insulin works quickly to lower blood glucose. It is a synthetically-designed analog of human insulin, similar but with a slight change in the chemical structure. Rapid insulin mimics the way insulin secreted by the pancreas works at meal time in a person who does not have diabetes. Generally, rapid acting insulin will:
- Start working 10 to 15 minutes after injection.
- Reach maximum effectiveness 30 to 90 min after injection.
- Last for three to five hours.
Rapid-acting insulin is usually taken before each meal, called a bolus dose, to help prevent spikes in blood glucose levels after eating. Because this insulin starts working so quickly, patients with diabetes must eat within a few minutes of injection to prevent hypoglycemia, or low blood sugar.
Rapid insulin is available from three different drug companies. Novo Nordisk makes Novolog, also known as insulin aspart. Patients taking Novolog are recommended to eat within 5 to 10 minutes of the injection. Humalog is insulin lispro, and is made by Eli Lilly and Company. According to the prescribing information, Humalog should be taken 15 minutes before a meal or immediately afterwards. Apidra, called insulin glulisine, comes to the market from Sanofi-Aventis. Apidra should be taken within 15 minutes before starting a meal or 20 minutes afterward.
All three of these rapid insulins can be taken via syringe or insulin pump, and are also available in an injectible pen device.