Insulin mixing involves drawing two different types of insulin into a single syringe before injection to simplify daily blood glucose management. This technique combines fast-acting insulin for immediate meal coverage with longer-acting insulin for sustained background control, reducing the total number of daily injections. Precision and safety are paramount; errors in mixing order or dosage can significantly alter the insulin’s intended action and lead to unsafe blood sugar levels. This procedure must only be undertaken after receiving explicit instruction and approval from a qualified healthcare provider.
Identifying Compatible Insulin Types
The mixing procedure traditionally involves combining an intermediate-acting insulin, specifically Neutral Protamine Hagedorn (NPH), with a short-acting or rapid-acting insulin. NPH insulin appears cloudy due to its suspension of zinc and protamine and provides a sustained effect over many hours. The clear insulin is typically a short-acting Regular insulin or a rapid-acting analog, intended to cover immediate glucose needs.
The rule of compatibility is restrictive, focusing mainly on the NPH type. Modern, long-acting insulins, such as insulin glargine (Lantus, Basaglar) and insulin detemir (Levemir), must not be mixed with any other insulin type. Mixing these can destabilize their specialized, slow-release mechanism, compromising effectiveness and causing unpredictable blood sugar fluctuations. Pre-mixed insulin products that already contain two types of insulin should also never be mixed with additional insulins. Before mixing, confirm that both vials are compatible, ideally from the same manufacturer, to prevent chemical incompatibility caused by differing buffers and preservatives.
Step-by-Step Procedure for Mixing Insulins
Properly mixing two insulins requires a sequential, four-step process to prevent contamination of the clear insulin vial. The first step involves preparing the intermediate-acting NPH insulin by gently rolling the vial between the palms of the hands for approximately 10 to 20 seconds. This action ensures the cloudy suspension is evenly mixed without creating air bubbles, which can occur if the vial is shaken vigorously. The tops of both insulin vials should then be wiped with an alcohol swab to sterilize the surface before piercing the rubber stopper.
The next phase is to inject air into both vials, starting with the cloudy NPH insulin first, to equalize the pressure inside the vacuum-sealed containers. Fill the syringe with air equal to the prescribed NPH dose and inject it into the NPH vial without drawing medication, then remove the needle. Next, fill the syringe with air equal to the dose of the clear, fast-acting insulin and inject it into that vial, keeping the needle in place. Introducing air into the cloudy vial first ensures the needle does not contaminate the clear vial with traces of NPH.
The third stage is the withdrawal of the clear insulin, which must be done while the needle is still in the vial. Invert the clear insulin vial and syringe, and draw the exact prescribed dose of the clear, fast-acting insulin into the syringe. Check the syringe for any air bubbles and remove them by gently flicking the barrel. If too much clear insulin is accidentally drawn, the entire syringe must be discarded and the process restarted, as the excess cannot be pushed back into the vial without contamination.
The final step is to withdraw the cloudy NPH insulin into the same syringe, completing the mixing process. Remove the needle from the clear vial and insert it into the cloudy NPH vial, which is then inverted. Draw the precise amount of NPH insulin into the syringe, adding to the clear insulin already present until the total prescribed units are in the syringe. This sequence, often remembered as “Cloudy, Clear, Clear, Cloudy” (Air into Cloudy, Air into Clear, Draw Clear, Draw Cloudy), prevents the cloudy NPH from entering and altering the clear insulin vial, which could compromise the clear insulin’s rapid action for future uses.
Essential Safety Rules and Post-Mixing Handling
Safety protocols extend to the immediate handling and administration of the final mixture. The mixed insulin dose must be injected immediately, typically within five to fifteen minutes of being drawn into the syringe. This urgency is necessary because the clear, fast-acting insulin begins to bind to the protamine in the NPH suspension once mixed, quickly altering the onset and peak action of the clear component.
Before injecting, check for air bubbles, as small air pockets can displace a measurable amount of insulin, leading to an inaccurate dose. Remove air bubbles by gently tapping the side of the syringe barrel to make them rise, then carefully pushing the plunger to expel the air while ensuring no insulin is lost. The correct equipment is also non-negotiable; users must only utilize sterile U-100 insulin syringes, which are calibrated specifically for the concentration of insulin typically found in vials.
After the injection is complete, proper disposal prevents accidental needlesticks. The used syringe and needle should never be recapped or bent and must be placed immediately into a designated puncture-proof container, such as a sharps container. Individuals should visually inspect the insulin both before and after mixing for any warning signs of degradation. Discoloration, cloudiness in the clear insulin, or the presence of lumps, flakes, or particulate matter indicates spoilage, and the insulin should be discarded.