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What is Insulin?

Insulin is a natural hormone secreted by the cells of the pancreas whenever glucose levels in the blood are increased. Insulin attaches to cells that use glucose for energy and stimulates it to uptake glucose from the blood.

Whenever insulin secretion or insulin-cell receptor sensitivity is impaired, synthetic insulin is needed to continue the function of natural insulin and maintain life.

Unfortunately, synthetic insulin cannot reverse abnormal insulin conditions and is thus needed by patients throughout his or her lifetime.


Synthetic insulin is required in patients suffering from:

  • Type 1 Diabetes
  • Type 2 Diabetes if other measures such as lifestyle change and oral drug therapy can’t anymore adequately maintain the blood glucose levels

Types of Insulin

Type Insulin Onset Peak (h) Duration Color Nursing Considerations
Rapid-Acting Lispro, Aspart, Glulisine <15 min 1-2 3-5 Clear Clients must eat a meal within 10-15 minutes of injection
Short-Acting Regular 0.5-1 h 2-4 3-8 Clear

Only insulin that can be administered through IV

Should be given 30 – 45 minutes prior to meals

Intermediate Acting NPH 2-4 h 5-8 12-18 Cloudy Pre-filled syringes should be stored in the refrigerator with needle tips up
Long Acting Determir, Glargine 2-4 h Peakless 20-24 Clear Don’t mix with any other insulin or solution
Premixed 2-4 h Peakless 20-24 Cloudy

Rapid-acting Mixture: client must eat within 15 minutes of injection

Short-acting mixture: client should eat within 30 minutes of injection

Don’t mix with any other insulin

What does the peak hour mean?

The peak hour of each type of insulin is the time when hypoglycemia symptoms usually occur.

For instance, if you give a rapid acting insulin at 0800h, then you must look for hypoglycemia symptoms between 0900h-1000h since its peak hour is 1-2 hrs from the time of administration.

Hypoglycemia symptoms to note for include:

  • hunger
  • decreased levels of consciousness
  • hunger
  • diaphoresis
  • weakness
  • dizziness
  • tachycardia

Insulin Administration: Mixing Insulin

Let’s take this scenario as an example:

Doctor orders to give a mixture of 3 units of regular insulin (clear) and 2 units of NPH (cloudy).

Method 1

  1. Add a total of 5 units of air to the syringe
  2. Withdraw 3 units of clear insulin
  3. Change the needle
  4. Withdraw 2 units of cloudy insulin

Method 2

  • If the needle cannot be changed, add a total of 5 units of air to the syringe
  • Withdraw 3 units of clear insulin
  • Withdraw 2 units of cloudy insulin

These methods will prevent the clear solution being contaminated by the cloudy one. If the short-acting medication was contaminated by the intermediate-acting one, masking effect could occur which could be fatal for the client.

Mixing Insulin Clear Before Cloudy
Mixing Insulin Clear Before Cloudy

When mixing insulin just remember: a clear day is preferable to a cloudy day.

Key Points

  • Blood glucose must always be tested prior to administration.
  • Insulin is never to be administered to an already hypoglycemic client.
  • CLEAR insulin must be withdrawn first prior to CLOUDY insulin when mixing insulin.
  • The peak hour of each type of insulin is the time when hypoglycemia symptoms usually occur.
  • Regular insulin is the only insulin that can be given through IV.  All other insulin types are given through subcutaneous injection.