Insulin is a drug that is used to control glucose in patients with diabetes mellitus. It is the only parenteral antidiabetic agent available for exogenous replacement of low levels of insulin.

Insulin is the hormone produced by the pancreatic beta cells of the islets of Langerhans. It is released into circulation when the levels of glucose around the cells arise. Insulin circulates through the body and reacts with specific insulin receptor sites to stimulate the transport of glucose into cells to be used for energy (facilitated diffusion).

Originally prepared from pork and beef pancreas, virtually all insulin is prepared by recombinant DNA technology now. This is a purer form of insulin and is not associated with sensitivity problems that many patients developed with the animal products.

Disease Spotlight: Diabetes Mellitus

  • Diabetes Mellitus (literally, “honey urine”) is a condition wherein there is a complex disturbance in the metabolism of carbohydrates, proteins, and fats. This alteration results in thickening of the layer below the endothelial lining of the blood vessels. This, in turn, causes narrowing, vessel remodeling, and decreased blood flow through vessels.
  • Most frequent clinical signs include hyperglycemia (fasting blood sugar of >106 mg/dL) and the presence of sugar in the urine (glycosuria).
  • Diabetes is classified into two: type 1 and type 2. Type 1 diabetes is common in younger people and is connected with cases of viral destruction of beta cells of the pancreas. On the other hand, type 2 is adult-onset and is associated with not enough insulin to maintain glucose control.
  • Hyperglycemia (high blood sugar) results when there is an increase in glucose in the blood. Clinical signs and symptoms include fatigue, lethargy, irritation, glycosuria, polyphagia, polydipsia, and itchy skin (from the accumulation of wastes that liver cannot clear).
  • Hypoglycemia is a blood glucose concentration lower than 40 mg/dL and can occur in many clinical situations like starvation and overtreatment of hyperglycemia. Manifestations include headache, paresthesias, hunger, and diaphoresis.

Therapeutic Action

The desired and beneficial action of insulin is:

  • Insulin replaces endogenous insulin. It is the only parenteral antidiabetic agent available for exogenous replacement of low levels of insulin. It reacts with the receptors of the cells to facilitate transport of various metabolites and ions across cell membranes and stimulates the synthesis of glycogen from glucose, of fats from lipids, and of proteins from amino acids.


Insulin is indicated for the following medical conditions:

  • Treatment of type 1 diabetes
  • Treatment of type 2 diabetes when other agents have failed
  • Short-term treatment of type 2 diabetes during periods of stress
  • Management of diabetic ketoacidosis, hyperkalemia, and marked insulin resistance


Here are the characteristic interactions of insulin and the body in terms of absorption, distribution, metabolism, and excretion:

Regular30-60 min2-4 h6-12 h
NPH (Humulin N)1-1.5 h4-12 h24 h
Ultralente (Humulin Ultralente)4-8 h10-30 h20-36 h
Lispro (Humalog)<15 min30-90 min2-5 h
Aspart (Novolog)10-20 min1-3 h3-5 h
Glargine (Lantus)60-70 minNone24 h
Glulisine (Apidra)2-5 min30-90 min2 h
Detemir (Levemir)1-2 h3-6 h5.7-23.3 h
T1/2: varies with each preparation
Metabolism: cellular level
Excretion: –

Contraindications and Cautions

The following are contraindications and cautions for the use of insulin:

  • No contraindications as it is a replacement hormone. However, close monitoring is needed among pregnant and lactating women to adjust the dose accordingly. It is the drug of choice for management of diabetes during pregnancy.
  • Insulin does enter breast milk but it is destroyed in the GI tract and does not affect the nursing infant.
  • Insulin-dependent mothers may have inhibited milk production because of insulin’s effects on fat and protein metabolism.

Adverse Effects

Use of insulin may result in these adverse effects:

  • hypoglycemia and ketoacidosis
  • local reactions at the injection site (lipodystrophy).


The following are drug-drug interactions involved in the use of insulin:

  • MAOIs, beta blockers, salicylates, alcohol. Increased glucose reduction
  • Beta blockers. Blocking the SNS also blocks many of the signs and symptoms of hypoglycemia, hindering the patient’s ability to recognize problems.
  • Various herbal therapies (juniper berries, ginseng, garlic, fenugreek, coriander, dandelion root, celery). Increased risk of developing hypoglycemia.  

Nursing Considerations

Here are important nursing considerations when administering insulin:

Nursing Assessment

These are the important things the nurse should include in conducting assessment, history taking, and examination:

  • Assess for contraindications or cautions (e.g. history of allergy, pregnancy, etc.) so that appropriate monitoring and dose adjustments can be completed.
  • Perform a physical assessment to establish a baseline before beginning therapy.
  • Assess skin lesions; orientation and reflexes; blood pressure, pulse, respiration and adventitious breath sounds which could indicate a response to high or low glucose levels and potential risk factors in giving insulin.
  • Inspect skin areas that will be used for injection; note any areas that are bruised, thickened, or scarred, which could interfere with insulin absorption and alter anticipated response to insulin therapy.
  • Obtain blood glucose levels as ordered to monitor response to insulin.
  • Assess activity level, including amount and degree of exercise which can alter serum glucose levels and need for these drugs.
  • Monitor the results of laboratory tests, including urinalysis, for evidence of glucosuria.

Nursing Diagnoses and Care Planning

Here are some of the nursing diagnoses that can be formulated in the use of this drug for therapy:

  • Risk for unstable blood glucose related to ineffective dosing of antidiabetic agents
  • Imbalanced nutrition: less than body requirements related to the use of insulin and underlying disease process
  • Risk for infection related to glucose levels

Nursing Implementation with Rationale

These are vital nursing interventions done in patients who are taking insulin:

  • Ensure that patient has dietary and exercise regimen and using good hygiene practices to improve the effectiveness of the insulin and decrease adverse effects of the disease.
  • Monitor nutritional status to provide nutritional consultation as needed.
  • Gently rotate the vial containing the agent and avoid vigorous shaking to ensure uniform suspension of insulin.
  • Rotate injection sites to avoid damage to muscles and to prevent subcutaneous atrophy.
  • Monitor response carefully to avoid adverse effects.
  • Always verify the name of the insulin being given because each insulin has a different peak and duration, and the names can be confused.
  • Use caution when mixing types of insulin; administer mixtures of regular and NPH insulins within 15 minutes after combining them to ensure appropriate suspension and therapeutic effect.
  • Store insulin in a cool place away from direct sunlight to ensure effectiveness. Predrawn syringes are stable for 1 week if refrigerated.
  • Monitor patient’s food intake and exercise and activities to ensure therapeutic effect and avoid hypoglycemia.
  • Monitor patient’s sensory losses to incorporate his or her needs into safety issues, as well as potential problems in drawing up and administering insulin.
  • Provide good skin care and foot care, to prevent the development of serious infections and changes in therapeutic insulin doses.
  • Provide comfort measures to help patient cope with drug effects.
  • Provide patient education about drug effects and warning signs to report to enhance patient knowledge and to promote compliance.   


Here are aspects of care that should be evaluated to determine the effectiveness of drug therapy:

  • Monitor patient response to therapy (stabilization of blood glucose levels).
  • Monitor for adverse effects (hypoglycemia, ketoacidosis, injection-site irritation).
  • Evaluate patient understanding on drug therapy by asking the patient to name the drug, its indication, and adverse effects to watch for.
  • Monitor patient compliance to drug therapy.

Practice Quiz: Insulin

Here are some practice questions for this study guide. Please visit our nursing test bank page for more NCLEX practice questions.

1. Which of the following statements are true about insulin?

A. It can be taken orally or injected subcutaneously to control high glucose level in the blood
B. It is an endogenous replacement for low insulin levels in patients with diabetes mellitus
C. It acts on various insulin receptor sites to facilitate entry of glucose into the cells
D. It should be avoided in pregnant patients with diabetes

1. Answer: C. Acts on various insulin receptor sites to facilitate entry of glucose into the cells

It is the insulin’ mechanism of action to control hyperglycemia. It is in parenteral form only and is an exogenous replacement for low insulin levels. Lastly, insulin is the treatment of choice in pregnant patients with diabetes.

2. Andrea, a 15-year-old patient, was newly diagnosed with diabetes type 1. She is on regular insulin. If she’s prescribed to have a daily shot of insulin every 8:30 am, when would be the appropriate time that she should have her meals?

A. 9:00 AM
B. 11:00 AM
C. 12:00 NN
D. 1:00 PM

2. Answer: A. 9:00 AM.

The onset of regular insulin is 30-60 minutes. Andrea should be able to eat by that time to avoid hypoglycemia.

3. Which of the following herbal therapies may increase the risk of hypoglycemia in patients prescribed with insulin?


A. Aloe vera
B. Ginseng
C. Papaya
D. All of the above

3. Answer: B. Ginseng

Others include juniper berries, garlic, fenugreek, coriander, dandelion root, celery.

4. All of the following nursing interventions are needed for patients taking insulin, except:

A. Administering refrigerated pre-drawn syringes as old as 1 week.
B. Administering mixtures of insulins within 15 minutes after combining them.
C. Rotating injection sites.
D. Shaking the vial to ensure uniform suspension.

4. Answer: D. Shaking the vial to ensure uniform suspension

Gently rotating the vial instead of shaking it will ensure uniform suspension. Options A and B are correct. Rotation of injection sites will prevent lipodystrophy.

5. A diabetic patient receiving insulin is in need of an antihypertensive. Which of the following would be the least recommended in the following choices?

A. Propranolol
B. Enalapril
C. Hydrochlorothiazide
D. Nifedipine

5. Answer: A. Propranolol

Propranolol is a beta-blocker and it can also block the signs and symptoms of hypoglycemia. Careful assessment is needed if this is to be given as well as other methods to identify hypoglycemia.

Recommended Resources

Recommended resources and reference books. Disclosure: Includes Amazon affiliate links.

  1. Focus on Nursing Pharmacology – Easy to follow guide for Pharmacology
  2. NCLEX-RN Drug Guide: 300 Medications You Need to Know for the Exam – Great if you’re reviewing for the NCLEX
  3. Nursing 2017 Drug Handbook (Nursing Drug Handbook) – Reliable nursing drug handbook!
  4. Lehne’s Pharmacology for Nursing Care – Provides key information on commonly used drugs in nursing
  5. Pharmacology and the Nursing Process – Learn how to administer drugs correctly and safely!
  6. Pharm Phlash Cards!: Pharmacology Flash Cards – Flash Cards for Nursing Pharmacology

See Also

Here are other nursing pharmacology study guides:

Gastrointestinal System Drugs

Respiratory System Drugs

Endocrine System Drugs

Autonomic Nervous System Drugs

Immune System Drugs

Chemotherapeutic Agents

Reproductive System Drugs

Nervous System Drugs

Cardiovascular System Drugs

References and Sources

References and sources for this pharmacology guide for Insulin:

  • Karch, A. M., & Karch. (2011). Focus on nursing pharmacology. Wolters Kluwer Health/Lippincott Williams & Wilkins. [Link]
  • Katzung, B. G. (2017). Basic and clinical pharmacology. McGraw-Hill Education.
  • Lehne, R. A., Moore, L. A., Crosby, L. J., & Hamilton, D. B. (2004). Pharmacology for nursing care.
  • Smeltzer, S. C., & Bare, B. G. (1992). Brunner & Suddarth’s textbook of medical-surgical nursing. Philadelphia: JB Lippincott.

Iris Dawn is a nurse writer in her 20s who is on the constant lookout for latest stories about Science. Her interests include Research and Medical-Surgical Nursing. She is currently furthering her studies and is seriously considering being a student as her profession. Life is spoiling her with spaghetti, acoustic playlists, libraries, and the beach.