Insulin in the Treatment of Diabetes Mellitus

Original Editor - Ashton Randolph

Top Contributors - Lucinda hampton, Ashton Randolph and Amr Saleh  

Introduction[edit | edit source]

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Insulin is a hormone made by beta cells in the pancreas. When we eat, insulin is released into the blood stream where it helps to move glucose from the food we have eaten into cells to be used as energy.

  1. With type 1 diabetes, the body produces little or no insulin as the cells that produce insulin have been destroyed by an autoimmune reaction in the body. Insulin replacement by daily injections is required.
  2. With type 2 diabetes the body produces insulin but the insulin does not work as well as it should (referred to as insulin resistance). To compensate the body makes more but eventually cannot make enough to keep the balance right. Lifestyle changes can delay the need for tablets and/or insulin to stabilise blood glucose levels. When insulin is required, it is important to understand that this is just the natural progression of the condition.[1]

Administration[edit | edit source]

Insulin administration can be via subcutaneous, intravenous, and intramuscular routes. The route of administration usually depends on the patient condition and setting.

Subcutaneous route

  • The most widespread route of administration
  • Preferred by most patients due to its ease and convenience in administration.
  • Comes in the form of insulin syringes, pens, and pumps. It is an easy and convenient way for patients to self-administer.
  • Absorption of insulin varies depending on the part of the body into which is injected. The abdomen absorbs insulin the fastest and is the site used by most people. The buttocks and thighs are also used by some people[1].

Intravenous insulin used in cases requiring emergency treatment

  • In the hospital setting, especially when immediate and close monitoring of blood glucose levels is needed.
  • In patients with diabetic ketoacidosis, hyperosmolar hyperglycemic state, severe hyperkalemia, beta-blocker toxicity, and calcium channel blocker toxicity[2].

Intramuscular insulin use is rare and utilizes concentrated regular insulin.[2]

Vials should be refrigerated and the patient should inspect the bottle for any changes in the serum as well as checking the expiration date before use as that can decrease drug potency. Patients should consider keeping a spare vial of insulin with them in case of emergency.[3]

Different Preparations Insulin[edit | edit source]

With insulin therapy, the goal is to mimic the endogenous release of insulin. Different preparations of biosynthetic insulin are available to do so, and are classified by their onset, peak and duration.  

  • Rapid-acting insulins, such as Lispro, Aspart, and Glulisine, are quickly absorbed, with a faster onset and higher peak[4]. They are administered before or after meals to account for the high influx of glucose, to mimic endogenous insulin[5][6][7].
  • Intermediate and long-acting insulins, such as insulin Zinc, Isophane and Glargine, are absorbed slower, with a prolonged onset and lower peak[4]. They are advantageous in maintaining a constant background level of insulin throughout the day or night, and in between meals[8].
  • Mixtures of various types can also be tailored for specific cases to optimize glycemic control and minimize injections[4]. Dosage is not uniform when being prescribed and is highly variable to individual requirements.

Once injected, insulin is absorbed rapidly and is metabolized by the liver, spleen, kidneys and muscles[9].

Physiotherapy[edit | edit source]

Therapists should be of aware of the adverse effects that patients might experience:

  • Hypoglycemia, or low blood sugar, can occur with missing meals, intense exercise, or an excessive dose of insulin. The patient will present with extreme hunger, fatigue, irritability, cold sweats, trembling hands, intense anxiety, and confusion.
  • Diabetic ketoacidosis can occur with non-intake of insulin. The patient will exhibit polyuria, nausea, vomiting, and abdominal pain. This is a medical emergency as it can lead to shock, coma, or death[10].
  • If an insulin pump is being used, it needs to be closely monitored to ensure it is working properly as improper amounts of insulin administration can lead to adverse side effects.
  • With repeated injections, there is a possibility of injection site irritation or hypersensitivity[10].
  • Polypharmacy needs to be observed as well. Insulin can have drug interactions with other prescription drugs that can impact insulin’s effectiveness. Beta blockers, Clonidine and Reserpine can hide signs of hypoglycemia. Corticosteroids, thyroid supplements and estrogens increase the needs for therapy. Alcohol, MAO inhibitors, and ACE inhibitors decrease the need for insulin. Glucosamine can also make blood glucose control more difficult[9].

Monitoring[edit | edit source]

Insulin has a low therapeutic index (the larger the therapeutic index the safer the drug is) and blood glucose levels require regular monitoring to avoid adverse effects like hypoglycemia.

Patient education should be provided about symptoms of hypoglycemia so that they can take immediate action when necessary. Monitoring for glucose levels is usually performed by fingerstick blood glucose test or glucose sensor device, both of which give instantaneous readings of blood glucose levels. Other tests, such as hemoglobin-A1c, can estimate glucose control over the past three months and enable insulin adjustment accordingly.

Back to Pharmacological Management of Diabetes Mellitus[edit | edit source]

References[edit | edit source]

  1. 1.0 1.1 Diabetes Australia Insulin Available: 25.9.2021)
  2. 2.0 2.1 Thota S, Akbar A. Insulin. StatPearls [Internet]. 2021 Jul 16.Available: (accessed 25.9.2021)
  3. American Diabetes Association. (2003). Insulin administration. Diabetes care, 26(suppl 1), s121-s124.
  4. 4.0 4.1 4.2 Donner, T. (2015). Insulin–pharmacology, therapeutic regimens and principles of intensive insulin therapy.
  5. Cox SL. Insulin glulisine. Drugs Today. 2005;41:433–440.
  6. Oiknine R, Bernbaum M, Mooradian AD. A critical appraisal of the role of insulin analogues in the management of diabetes mellitus. Drugs. 2005;65:325–340.
  7. Vazquez-Carrera M, Silvestre JS. Insulin analogues in the management of diabetes. Methods Find Exp Clin Pharmacol. 2004;26:445–461.
  8. Davis SN. Insulin, oral hypoglycemic agents, and the pharmacology of the endocrine pancreas. In: Brunton LL, et Al, eds. The Pharmacological Basis of Therapeutics. 11th ed. New York: McGraw-Hill; 2006.
  9. 9.0 9.1 Ciccone, C. D. (2013). Davis's Drug Guide for Rehabilitation Professionals. Philadelphia: F.A. Davis Company.
  10. 10.0 10.1 Alotaibi, A., Al Sultan, B., Buzeid, R., Almutairi, M., Alghamdi, E., Aldhaeefi, M., & Albareqi, M. (2018). An overview of insulin therapy in pharmacotherapy of diabetes mellitus type I. International Journal Of Community Medicine And Public Health, 5(3), 834-838.