2 Insulin Therapy

Insulin plans and roles

Insulin formulations act at different speeds and for different lengths of time. An insulin plan, including doses and timing, must follow the individual prescription and the instructions for the specific product. Never change or substitute an insulin dose or type without guidance from the prescribing clinician.

Basal and mealtime coverage

In a basal–bolus plan, basal insulin helps control glucose between meals and overnight. Mealtime insulin covers food-related glucose rises and may include a correction dose if that is part of the prescribed plan.

People with type 1 diabetes need ongoing insulin, including basal coverage, even when they are not eating. Illness or fasting calls for an individualized plan; do not stop insulin independently.

Timing insulin with meals

Coordinate mealtime insulin with food and follow the prescribed timing for the specific insulin. Rapid-acting products are generally coordinated with meals, but exact timing varies by formulation and prescription; do not apply one timing rule to every insulin.

Regular human insulin is commonly taken about $30$ minutes before a meal, unless the person’s specific instructions say otherwise. Confirm timing with the product instructions and prescribing clinician.

If a meal is unexpectedly delayed after a prescribed rapid-acting mealtime dose, follow the established delayed- or missed-meal care plan and check glucose as directed. If unsure, seek help rather than guessing or repeating the dose. Mealtime insulin without the expected food can lead to hypoglycemia; do not independently stop basal insulin.

Product checks and injection practices

Before each injection, check the insulin product name and prescribed dose. Insulin mix-ups can cause serious harm, so do not identify a product by pen color alone or assume that different pens contain the same concentration. Follow the storage, expiration, and in-use instructions for the specific product.

Use insulin as directed and never share insulin pens or needles. For injections, use appropriate subcutaneous sites and rotate injection points within an appropriate body area. This helps reduce injection-site problems and support more consistent absorption. Avoid injecting into muscle, scars, or damaged skin.

Monitoring and correction doses

Monitor glucose as directed and follow the prescribed correction plan. A rapid-acting correction dose may still be working shortly after it is given. Repeating a dose too soon can cause insulin stacking and a later low, so account for insulin still active and follow the prescribed correction schedule rather than immediately repeating a full dose.

Responding to low blood glucose

For an alert person who can swallow and has a glucose reading of $62\ \text{mg/dL}$ ($3.4\ \text{mmol/L}$), the usual 15–15 approach is to take $15\ \text{grams}$ of fast-acting carbohydrate, recheck glucose after $15\ \text{minutes}$, and repeat if it is still below $70\ \text{mg/dL}$ ($3.9\ \text{mmol/L}$. Individual instructions may differ, including for children.

If a person is unconscious and severe hypoglycemia is suspected, treat it as a medical emergency. Give prescribed glucagon if available, call emergency services, and give nothing by mouth because of choking risk.

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