Problems With Mixed Insulin Therapy


First, let me say that this post is not medical advice, nor is it designed for anyone personally. Making any type of change to your insulin regimen is something you should discuss with your primary healthcare provider. This post is meant to be a discussion of the common problems with mixed insulin therapies and how to possibly address them. You can use these concerns as a basis for discussion with your healthcare provider.

For a complete discussion of insulin therapy, please see my page “Using Insulin” HERE:

As I briefly discussed in this link, there are basically two benefits to mixed insulin therapy:

  • Cost, and
  • Ease of use.

But for control, it is not the best option.

Mixed insulins can have their place.  For instance, they are ideal for those that can only afford one vial of insulin at a time.  Or for those with limited abilities in calculating and managing their insulin doses.  They may be ideal for those that are advanced in years or those with limited dexterity, limited understanding, or even vision problems (people that may mix up insulin vials if they have more than one.)  However, if you are not bound these types of circumstances, you may consider a different, more effective regimen.

First if all, with mixed insulin, the ratios are fixed. For instance, with 70/30 insulin, you get 70% intermediate acting (used as basal) and 30% short acting (used as bolus). You can’t change the ratios. So if you need more short acting, for instance, you HAVE to take more intermediate acting too. Not ideal.

Next, because the N portion of the insulin lasts about 1/2 a day, you can’t take a mixed injection at lunch, which may result in elevations. (A lunch meal may possibly be covered by a peak in “N” insulin but this is often unpredictable.  Therefore, some people add an R injection before lunch to address this.)

But overall, it is my opinion that it is best to split insulins up and mix them yourself. They can be mixed in the same syringe (see how to HERE). That means buying a separate vial of R and N.

If your insurance covers analog insulins (or if you can afford them), many feel they are better for the simple fact that they are a little more predictable and the true basal insulins are “peakless” (N insulin has unpredictable “peaks” that could cause low BG.) But you can still work with N and R. I would, however, suggest splitting them up. How do you do that?

For instance, if you are currently getting, say, 20 units of 70/30 twice per day, that means you are getting 14 units of N and 6 units of R twice per day. If you split them up, you can use those doses as a starting point. If you are high (or low) at FASTING and BEFORE meals, this indicates that you need more (or less) N insulin. If you are high (or low) AFTER meals, this indicates that you need more (or less) R insulin. (R should be taken AT LEAST 30 minutes before a meal.) Your mid-day meal might also need to be covered with R insulin (but possibly not as much, as your N insulin might be “peaking” at that time.) Seems a bit confusing, but this is what comes with the territory in dealing with N and R insulins.

Changing to analog insulins (rapid acting and long acting) is often more predictable, as rapid acting typically last only about 4 – 5 hours (getting you from meal to meal), and long acting insulins have no “peaks” to deal with. These insulins cannot be mixed in the same syringe, however, so this would require 4 (possibly 5) injections daily.

If you have some time, HERE is a good video explaining the different insulin types and how to manage them. It also talks about how to figure out your “carb ratio” and “sensitivity factor” (or “correction factor.”)  These are concepts that everyone taking insulin should thoroughly understand.  This person does not appear to endorse a low carb lifestyle, but the information with graphics might be very helpful to you.

Once again, before making any changes to your insulin regimen, discuss it with your primary healthcare provider.