NovoLog Mix 70/30 is a premixed insulin that combines two forms of insulin aspart in a single injection: 70% intermediate-acting insulin and 30% rapid-acting insulin. It’s designed to cover both mealtime blood sugar spikes and background insulin needs between meals, reducing the number of injections a person with diabetes needs each day.
How the Two Components Work Together
The “70/30” in the name refers to the ratio of the two insulin types inside. Seventy percent of the mixture is insulin aspart protamine, a crystallized form that absorbs slowly and provides a steady baseline of insulin over several hours. The remaining 30% is soluble insulin aspart, which enters the bloodstream quickly to handle the rise in blood sugar that follows a meal.
This combination means you get two layers of blood sugar control from one shot. The rapid-acting portion starts working within 10 to 20 minutes and handles the immediate spike from eating, while the intermediate-acting portion continues working for up to 24 hours to keep levels more stable between meals and overnight. Peak activity generally falls somewhere between 1 and 4 hours after injection.
Who Uses It
NovoLog Mix 70/30 is prescribed for adults with type 1 or type 2 diabetes who need both mealtime and background insulin coverage. It’s especially common for people with type 2 diabetes who have progressed beyond oral medications alone but want to keep their injection schedule simple. Instead of taking a long-acting insulin plus a separate rapid-acting insulin at meals, one premixed injection can handle both roles.
The tradeoff is flexibility. With separate insulins, you can adjust your mealtime dose independently from your background dose. A premixed product locks those two amounts into a fixed ratio, which works well for people with predictable eating schedules but can be limiting if your meals vary significantly in size or timing.
How to Inject It
NovoLog Mix 70/30 is injected under the skin (subcutaneously), typically within 15 minutes before a meal. It should never be given intravenously or used in an insulin pump.
The insulin comes as a cloudy suspension, so it needs to be mixed before every injection. For a vial, roll it gently between your palms in a horizontal position at least 10 times. For the FlexPen, roll it between your palms 10 times, then turn the pen upside down and back at least 10 more times so the small glass ball inside moves from end to end. Keep going until the liquid looks uniformly white and cloudy. If clumps remain or particles stick to the sides, don’t use it.
Common injection sites include the abdomen, upper arm, and thigh. Rotating your injection site with each dose helps prevent the skin from developing lumps or thickened areas, which can interfere with how well the insulin absorbs. You can inject in the same general region (the abdomen, for instance) but shift the exact spot by at least an inch each time.
What Not to Do With It
Do not mix NovoLog Mix 70/30 with any other insulin products. It’s already a blend, and adding another insulin could alter the ratio and change how it works. Do not draw it into the same syringe with another insulin. Do not use it in an insulin infusion pump. And do not inject it into a vein; it is designed for subcutaneous injection only.
Side Effects
Low blood sugar (hypoglycemia) is the most common side effect of any insulin therapy, including NovoLog Mix 70/30. Signs include shakiness, sweating, a fast heartbeat, dizziness, and confusion. Keeping a fast-acting sugar source on hand, like glucose tablets or juice, is standard practice for anyone using insulin.
Injection site reactions, including redness, swelling, or itching, occurred in about 7% of patients using NovoLog Mix 70/30 in clinical trials, compared to 5% on an older premixed insulin. These reactions were mild enough that fewer than 1% of people stopped using the medication because of them. Allergic reactions affecting the whole body are rare but possible.
Storage
Unopened vials and FlexPens should be stored in the refrigerator (36°F to 46°F). Once you start using a vial or pen, it can be kept at room temperature, between 59°F and 86°F, for up to 28 days. After 28 days at room temperature, discard it even if insulin remains. Never freeze it, and keep it away from direct heat or sunlight.
NovoLog Mix 70/30 vs. Regular NovoLog
Regular NovoLog (insulin aspart) is a pure rapid-acting insulin used to cover meals. It works fast, peaks quickly, and is out of your system within a few hours. NovoLog Mix 70/30 pairs that same rapid-acting insulin with a longer-lasting form, so it covers meals and provides background insulin in one shot. If your provider has prescribed one, they are not interchangeable with the other, because the dosing, timing, and blood sugar effects are quite different.