Which needle size is most appropriate for administering an intradermal injection?

A. Administer insulin glargine and insulin lispro separately using two different syringes: Insulin glargine is a long-acting insulin that should never be mixed with other insulins, including rapid-acting insulins like lispro. Administering them separately ensures accurate dosing and maintains the intended pharmacokinetic profiles of both insulins.

B. Mix both insulins in a single syringe after warming them to room temperature: Mixing insulin glargine with lispro can alter the absorption and effectiveness of glargine, potentially leading to unpredictable blood glucose control. Warming to room temperature does not prevent this interaction.

C. Draw up insulin lispro first, then insulin glargine into the same syringe: Even if lispro is drawn first, mixing it with glargine in one syringe is unsafe. The chemical properties of glargine prevent it from being combined with other insulins without affecting its basal action.

D. Draw up insulin glargine first, then insulin lispro into the same syringe: Drawing glargine first does not make it safe to mix with lispro. Glargine must always be administered separately to maintain its long-acting effect and avoid dosing errors or hypoglycemia.

Calculation:

Ordered Dose: 40 mg

Available Concentration: 10 mg/mL

• Set up dimensional analysis

Formula: Volume to administer = (Ordered Dose × Conversion Factor)

Conversion Factor = 1 mL ÷ 10 mg

• Perform the calculation

Volume to administer = 40 × (1 ÷ 10)

Volume to administer = 4 mL