Diluting Insulin

So what exactly is diluting?  It's simply making insulin weaker. Why would you want to dilute?  Because insulin in its full-strength form is often too strong for infants, recently-diagnosed kids, or even some adults that are very sensitive to insulin.

With most doctors pushing massive amounts of carbs and insulin, diluting insulin has long been forgotten. However, it's a super useful tool for low carb eating, especially for small kids. Diluting allows you to give as small as a 0.1u dose accurately. It also allows you to do tiny corrections much sooner to avoid spikes.  For example, if 1u (unit) of Novolog/Humalog drops your child 300mg/dL, how would do correct a high of say 140mg/dL?  You couldn't safely without diluted insulin.  But with diluted insulin, you could safely and accurately dose 0.2u which would drop your child down to 80mg/dL which is EXACTLY in the middle of normal range for a child (normal for a child is 60 - 100mg/dL).

 

NovoNordisk makes a diluting medium (also called diluent) for Novolog, Novolin-R (aka "Regular"), and Levemir. Here is the NovoNordisk diluting medium:

Some of you with a keen eye will notice the diluent above states for use with Novolog only. But above I stated it can also be used for Novolin-R and Levemir too.  What's up with that?!  This took a TON (and I mean a TON!) of research to figure out.  The long story short is that the diluent they make isn't "marketed" to be used with Novolin-R and Levemir in the US, but it CAN be used. All 3 NovoNordisk insulins have the same pH therefore can all be diluted.  In fact, it is "marketed" as such in other countries and the box clearly states so.  Below is a picture I received from a friend in Australia that also lists Levemir.  Dr. Richard Bernstein confirmed this with NovoNordisk also!

Lilly makes a diluent for Humalog and Humulin-R. To my knowledge there is NO way to dilute Lantus basal insulin.  Here is the Lilly diluting medium:

For Novolog/Novolin-R/Levemir your pharmacist/doctor/RN calls NovoNordisk and asks for a "Diluent Form" to be faxed over (or print the copy I have below). They fill it out, fax it back, and NovoNordisk sends it to the pharmacy. It takes just a few days to get. 

 
For Humalog/Humulin-R, the pharmacist/doctor/RN can email a request to lilly_distribution@lilly.com or call 800-821-0538.  (Note: patients used to be able to email asking for the diluting medium to be sent to their pharmacy, but Lilly has stopped this practice and states a pharmacist, doctor, or RN must do it.  Every once in a while I hear of a patient still successfully doing this, but not very often anymore.)
 

Be prepared... you may have a hard time finding a pharmacy that even knows what diluent is because of today's massive insulin doses. Local, Mom & Pop type pharmacies are often the most accommodating. Compounding pharmacies will also usually know what it is.  Be persistent!

You can dilute right in the diluent bottle, but if you don't want to waste diluent, sterile empty vials can be provided by your pharmacy (mine does), you can order from medical supply companies, or even from Amazon. Ordering these doesn't require a prescription so you can get them from whatever source you choose.  Here's what they look like:

Once you have diluting tools in hand, you can dilute insulin to whatever strength you want.  My favorite diluting ratio is 4:1, which means you have 4 parts diluent and 1 part insulin (5 parts in total - remember this "5 parts"... it will be important later).  Or another way to think if this ratio is that it's a 20% strength.  This works particularly well with syringes with half unit markings because each half unit that you draw up into the syringe, you're actually only dosing 0.1u of insulin.  So for example if you want to give a dose of 0.3u, then you'll draw up 1.5u into the syringe (0.3u x 5 parts = 1.5u).

 

The math to make a 4:1 ratio in a vial looks something like this:  Inject 400u of diluting medium into your empty vial.  Then inject 100u of insulin into the vial. (That's 4 parts diluting medium and 1 part insulin = 5 parts total.)  Gently swirl around to mix.  Depending on the size of your empty vial, that will make about a 1/4 of a vial of diluted insulin.  To make larger batches, you would inject 800u of diluting medium and 200u of insulin. Or 1200u of diluting medium and 300u of insulin. Get it?  It's not really about how much insulin or diluting medium you put in.  It's about keeping each to a 4:1 ratio.  You can make as little or as much as you want following this ratio.  Note: my pharmacy gives me large 3mL syringes to transfer this much insulin quickly.  Otherwise it will take a while.

 

Here is a video to show you how to do the actual diluting...  Diabetes University: Session 27 - Diluting Insulin

 

Now... what about those of you that use insulin pens/cartridges?  That can be diluted too!  You do have to do this a bit differently though.  Here's what I do:  

Draw out the amount of insulin needed from the cartridge (don't inject air) for whatever ratio you want to do. (I transfer what I draw out into my Novolog/Novolin-R vial to not waste it!). Then you inject the same amount of diluting medium that you drew out of insulin. When the syringe is still in the cartridge, pull the plunger out and it will release any extra pressure.

Roll and tip the pen around a few times to mix. A few air bubbles will get in there from the transfer process so you just do a few "airshots" to get excess air out.

 

Here are a couple of math examples.  Insulin pen cartridges are 3mL (which is 300 units) so keep that in mind as we do the math.  

 

If I want to make a 4:1 ratio for corrections (remember that is 5 parts total), I'll pull out 240u of insulin and put in 240u of diluting medium.  NovoPen Echo pens can dose in half unit increments, so just like in my example with vials above, for every half unit I dial, you're only dosing 0.1u of insulin.  So if I want to do a 0.4u correction, I would dial up 2u (because 0.4u x 5 parts = 2.0u)

Ok, now the Novolin-R Flex pens.  They unfortunately can only dose in 1u increments in the US.  But most kids aren't as sensitive to Regular insulin so being able to dose in half unit increments is usually small enough, so I'll do the math for a 1:1 ratio.  But if you need to dilute it more, by all means, do!  So to make a 1:1 ratio (2 parts in total), all I need to do is pull out 150u of insulin and put in 150u of diluting medium.  Now for every 1u that I dial up, only half a unit (0.5u) is being dosed.  So if I want to give a dose of 1.5u I would dial up 3u (because 1.5u x 2 parts = 3u).

Now... I acknowledge that having different insulins in different ratios can be confusing and it's important to keep them straight!  Our 'home' vials use a color coding system to visually keep them straight, so we use the same colors for our pens while we're on the go.  Since implementing this system, we've never accidentally mis-dosed!  Fingers crossed!

These are our "home" insulin vials:

 

And here are our "to-go" pens:

 

Here is the form your Pharmacist will call to get, fill out, and fax back to get your free NovoNordisk diluent and steps on what they must complete. (Updated 3/16/22)