1 Insulin Therapy

Insulin roles and timing

Insulin plans are individualized. Product instructions and the patient’s prescribed plan take precedence over general principles; practice examples should not be used to calculate or change a real patient’s dose.

Insulin types differ in how quickly they start working, when they peak, and how long they last. Onset, peak, and duration vary by product, so check the specific insulin’s instructions.

Match insulin to meals and background needs

Rapid-acting insulin is generally used for mealtime or correction coverage. Regular insulin, also called short-acting insulin, provides slower mealtime coverage. Intermediate-acting insulin provides background coverage with a more noticeable peak, while long- or ultra-long-acting insulin provides background coverage with little or no pronounced peak.

Mealtime insulin lowers glucose as food is absorbed, so coordinating its timing with food helps reduce the risk of glucose dropping too low. If a meal is unexpectedly delayed or skipped, follow the person’s individualized instructions or contact the diabetes care team; do not guess at a dose.

Monitor glucose

A blood glucose meter and a continuous glucose monitor (CGM) are common ways to monitor glucose. Extra monitoring may be needed around physical activity or when insulin doses, meals, or routines change, according to the care plan.

Respond to low glucose

For an awake person who can swallow, treat glucose below $70\,\text{mg/dL}$ with $15\,\text{g}$ of fast-acting carbohydrate. Wait $15$ minutes and recheck glucose; if it is still below $70\,\text{mg/dL}$, repeat the treatment. Follow the person’s specific plan if it differs, because children may need a different amount.

If someone is unconscious or cannot swallow safely, do not give food or drink by mouth. A trained helper may give prescribed glucagon, should call emergency services, and should stay with the person.

Rotate injection sites

Rotate injection spots to help avoid repeatedly using the exact same area. Common sites for subcutaneous insulin injections include the abdomen, thigh, upper arm, and buttock. Follow product and diabetes care-team instructions.

Verify the insulin and dose

If the insulin dose on a label differs from the written care plan, pause and clarify the discrepancy with the prescriber or pharmacist before giving the dose. Verify the patient, insulin name and type, concentration, prescribed dose in units, timing, and that the correct pen or syringe is being used.

Never convert or substitute insulin concentrations by guesswork. Changes in insulin strength, type, or delivery method can affect glucose control and hypoglycemia risk.

Avoid premature correction doses

Some insulin may still be active after a correction dose. Taking another correction too soon can cause insulin stacking and hypoglycemia. Follow the prescribed correction plan and account for active insulin as directed; do not improvise extra doses.