Diabetes mellitus is a condition that is characterised by low levels of insulin levels in the body due to reduced activity of beta cells of islets of Langerhans in the pancreas or abnormal uptake of the insulin by the receptors thereby increasing the glucose levels of blood. Diabetes mellitus is of type 1 and type 2 whereas type 2 is more predominantly seen. It is caused due to reduced insulin production by pancreatic cells.

Insulin is a hormone that counteracts glucose in the body and keeps the glucose levels at normal. But when insulin is low in the body as in the case of diabetes mellitus, externally the insulin has to be administered in the body if medication and dietary modifications don’t work.

Who requires insulin therapy?

• Patients whose diabetes mellitus condition is not manageable by Metformin or other antidiabetic medications.
• Patients who are hospitalised for any surgery or other conditions where glucose levels are very much raised.
• Old aged patients with diabetes mellitus in extreme cases.
• Very high levels of blood glucose.
• Diabetic ketoacidosis patient.
• Hyperglycaemic, hyperosmolar non ketotic coma patient.
• Patient with burns, and myocardial infarction.
• Patient with hyperkalemia ( insulin can be tried)

Types of insulin used in insulin therapy and insulin preparation.

• Conventional type Insulin is produced from the bovine pancreas or porcine pancreas. As it is obtained from the animal source it is quite impure as compared to other types. In developing countries like India, it is still in use.
• Highly purified insulin is obtained from the porcine pancreas itself but is very highly purified by various processes. The impure protein content is negligible and hence this is used in developed countries. 
• Insulin analog: small positional modifications of amino Acids are done to get an analog of insulin. They have better results than original insulin.
• Insulin mixtures: a combination of insulin with other components give mixtures.

Action and duration of action of different types of insulin.

• Conventional type: it is further divided on the bases of their time of action as short acting, intermediate acting, and long acting. 

Short acting: regular insulin, semilente insulin.

The onset of action: 30 minutes to 2 hours

Duration: 5 hours to 15 hours depending upon the type of insulin. Avg time is 2hrs.

Intermediate acting: Lente insulin, isophane insulin.

The onset of action: 2 hours.

Duration of action: 17-24hours.

              Long acting: protamine zinc insulin, Ultralente Insulin.

              The onset of action: 1 to 6 hours.

              Duration of action: 6 to 36 hours.

• Highly purified insulin: it is classified as single peak insulin and monocomponent Insulin.

Single peak: regular insulin, Lente insulin

Monocomponent insulin: regular and lente insulin.

• Insulin analog: it is further classified as rapid acting and long acting

Rapid acting: insulin lispro, insulin aspart

Long acting: insulin glargine, insulin detemir.

Insulin dosage.

• Conventional insulin: plane insulin: 100IU/ ml.
• Highly purified regular insulin: actrapid, lentard, monotard 40 IU/ml
• Insulin analog: humalog 100U/ml injection ( insulin lispro)
• Insulin analogue: flexpen 100 IU/ml ; Novolog 100 U/ ml injection ( insulin aspart).

How is insulin administered in the body?

• It is administered in the form of an injection.
• Route of administration is subcutaneous
• It can be self administered by the patient or patient care takers can inject it for the patient. Prior training and guidance have to be gained from a medical professional.

When to take insulin injections?

• It should be administered 20-30 minutes prior to lunch, and dinner.
• Insulin should be taken in injection form only as oral insulin is not of any considerable use.

Steps to administer insulin injections.

• Clean the area where the injection is to be given.
• Open the cap of the injection just before injection and do not keep the open syringe for a long duration.
• Look for any saturated material before injection, if any, do not use the medication.
• Inject the full dose as prescribed by the doctor at once.
• Dispose of the syringe with a closed cap.

What are the Devices used for insulin therapy?

• Insulin injections
• Insulin pumps
• Injection ports.

Advantages of insulin therapy.

• It can be administered by the patient himself or herself.
• It is readily available in the medical stores on prescription.
• It is easy to use.
• Meal times and injection times can be changed.
• It is portable and can be carried from place to place.
• It is less time consuming.
• Quicker action and bioavailability.
• Maintains better blood glucose levels.

Disadvantages of insulin therapy.

• It can cause hypoglycemia.
• It requires prior training before administration.
• It is the invasive route of administration.
• It May cause irritation and itching at the site of injection.
• Missing any dose causes shivering, fainting, or other issues related to hyperglycemia.
• Conventional insulin which is not pure can cause allergic reactions.
• Conventional insulin and insulin are not very stable.

Other points:

• Highly purified insulin should strictly be used in pregnancy In case of gestational diabetes.
• Neutral protamine hagedorn is another name for isophane insulin.
• In obese patients, the requirements for insulin are higher.
• Multiple doses may be required for different patient conditions.