NPH insulin may be mixed with both rapid-acting insulin analogs and fast-acting human Regular insulin. These mixtures include various combinations:

• In the United States, rapid-acting insulin, Lispro (humalog) is mixed with NPH in a 50:50 (50% NPH and 50% insulin Lyspro) and 75:25 (75% NPH and 25% insulin Lispro) ratio.
• Insulin/Aspart (Novolog) combinations also are available as 70:30 mixtures (70% NPH, 30% insulin aspart).
• The traditional NPH ratio of Regular pre-mixed insulin 70:30 (70% NPH, 30% Regular) is still available. These insulins are available as vials, and as insulin pens.

The benefit of pre-mixed insulin is that the fast- and long-acting insulin is combined. No mixing of the insulin is necessary, and there is only one injection.

The disadvantage is that NPH, which has a relatively unpredictable action, is the only long-acting insulin that can be used. Also, when the doses in a mixture is increased or decreased, the amount both of the short acting insulin and long-acting insulin changes, which increases the risk of both high and low blood sugars. Mixtures also don’t allow a separate correction to be made for high blood sugars.

(You may wonder why there are NO pre-mixed insulins using glargine, detemir and degludec. This is because insulin glargine, detemir and degludec cannot be mixed in the same syringe with other insulins!)

Pre-mixed insulins are usually prescribed for patients needing a simple insulin treatment plan, and sliding scale therapy.

You may be in this category if you:

• Are older, with regular meal and activity patterns
• Have diminished vision or trouble with dexterity
• Are just starting insulin therapy