How to Give Insulin
Insulin should be injected subcutaneously into the abdomen, thigh, buttock, or upper arm using the shortest available needles (4-mm pen needles or 6-mm syringe needles) at a 90-degree angle, with systematic rotation within the same anatomical area to prevent lipohypertrophy. 1
Injection Site Selection and Rotation
Approved injection sites include the subcutaneous tissue of the upper arm, anterior and lateral aspects of the thigh, buttocks, and abdomen (excluding a 2-inch radius around the navel). 1
- The abdomen has the fastest absorption rate, followed by arms, thighs, and buttocks—site selection should account for these differences in absorption kinetics. 1
- Rotate systematically within one anatomical area (e.g., rotating injections within the abdomen quadrant by quadrant) rather than switching between different body regions with each injection, as this reduces day-to-day variability in absorption. 1
- Inject at least 1 cm (approximately one adult finger width) from the previous injection site, rotating in a consistent direction within the chosen zone. 1
- Change zones weekly, using one quadrant or half of a body area per week. 1
- Avoid injecting into areas of lipohypertrophy (soft, raised areas of accumulated subcutaneous fat), as these sites show slower and erratic insulin absorption leading to glycemic variability and unexplained hypoglycemia. 1
Injection Technique
Use 4-mm pen needles or 6-mm syringe needles as first-line choice in all patient categories—these are safe, effective, less painful, and reduce the risk of intramuscular injection. 1, 2
Standard Technique:
- For most adults: Inject at a 90-degree angle perpendicular to the skin without pinching. 1, 3
- For thin individuals or children: Pinch the skin and inject at a 45-degree angle using short needles to avoid intramuscular injection, especially in the thigh area. 1
- Do not aspirate (drawing back on the syringe to check for blood)—this is unnecessary. 1
- Keep the needle embedded in the skin for at least 5-6 seconds after complete insulin delivery to ensure full dose administration, particularly with insulin pens. 1, 3
Critical Pitfall:
- Intramuscular injection must be avoided for routine insulin administration, as it causes faster and unpredictable absorption with increased risk of severe hypoglycemia—risk is highest in younger, leaner patients injecting into limbs with longer needles. 1
Needle Disposal and Reuse
- Remove the needle immediately after each injection without recapping to avoid needlesticks, and dispose in puncture-resistant sharps containers. 3
- Needle reuse is not recommended by manufacturers and is associated with lipohypertrophy, though patients who reuse needles should not be subjected to alarming claims of excessive morbidity. 2
Insulin Storage and Preparation
Unopened Insulin:
- Store in refrigerator at 2-8°C (36-46°F) without freezing—do not use if frozen. 3
- Keep in original carton to protect from light. 3
Opened Insulin:
- Vials: Keep refrigerated or at room temperature below 30°C (86°F) for up to 42 days; discard after 42 days even if insulin remains. 3
- Pens: Store at room temperature below 30°C (86°F) for up to 42 days—do not refrigerate pens in use; discard after 42 days. 3
- Allow insulin to reach room temperature (30-60 minutes out of refrigerator) before injecting, as cold insulin is painful and may contribute to lipohypertrophy. 1
Insulin Inspection:
- Use only if clear and colorless—do not use if cloudy, discolored, or contains particles (except for NPH insulin which should be gently rolled until crystals dissolve). 1, 3
- Do not shake vigorously, as this introduces air bubbles causing dosage errors. 3
- For cloudy insulins (NPH): Gently roll or tip the vial/pen until crystals dissolve—vigorous shaking is contraindicated. 1
Delivery Methods
Syringes and Vials:
- Remove tamper-resistant cap and wipe rubber membrane with alcohol swab. 3
- Pull plunger back to the number of units needed, inject air into vial. 3
- Invert vial and syringe, withdraw insulin to a few units beyond correct dose. 3
- Tap syringe to remove air bubbles, push plunger to correct marking. 3
- Inject immediately. 3
Insulin Pens:
- Perform an airshot before each injection per device instructions to ensure proper insulin flow. 3
- Attach a new needle immediately before each use and remove after injection. 3
- Keep needle under skin for at least 6 seconds after pushing plunger completely. 3
Insulin Pumps (CSII):
- Provide basal delivery of rapid-acting or ultra-rapid-acting insulin (generally 40-60% of total daily dose) with mealtime boluses for the remainder. 1, 4
- Change infusion sites every 2-3 days to reduce infection risk and prevent lipohypertrophy. 5, 4
- Automated insulin delivery (AID) systems are superior to sensor-augmented pump therapy for increasing time in range and reducing hypoglycemia. 1
Alternative Devices:
- Jet injectors inject insulin as a fine stream without needles—useful for needle-phobic patients but have high initial cost and may traumatize skin. 1
- Prefilled syringes are stable for 30 days refrigerated when stored vertically with needle pointing upward; roll between hands before administration. 1
Insulin Mixing Considerations
- Do not mix or dilute insulin glargine (Lantus) with any other insulin or solution due to its low pH—requires separate injections when combining basal and prandial insulin. 6, 3
- For other insulins that can be mixed: Draw clear (rapid/short-acting) insulin first, then cloudy (intermediate-acting) insulin into the same syringe. 1
- Consistency of technique and careful blood glucose monitoring are essential when premixing insulins. 1
Monitoring and Safety
- Daily fasting blood glucose monitoring is essential during insulin titration phases. 6
- Carry at least 15 grams of fast-acting carbohydrate at all times to treat hypoglycemia (blood glucose ≤70 mg/dL). 1
- Family members and caregivers should be trained in glucagon administration for severe hypoglycemia when oral carbohydrate cannot be given. 1
- Wear medical identification (bracelet or necklace) indicating insulin use. 1
- Examine injection sites regularly for lipohypertrophy, infection, or other complications—healthcare providers should assess injection technique at least annually. 1
Special Considerations
- Exercise increases absorption rate from injection sites due to increased blood flow—adjust timing or dosing accordingly. 1
- Increased skin temperature (sunbathing, hot water exposure) accelerates insulin absorption and may cause hypoglycemia. 1
- Avoid injecting into areas of lipohypertrophy, as absorption is slower and unpredictable. 1
- If blood appears after needle withdrawal, press lightly with a finger—do not rub the area. 3