Covering All the Bases When Prescribing Insulin: A Detailed 'How To'

Jay H. Shubrook, DO; Kim M. Pfotenhauer, DO


June 19, 2017

Jay H. Shubrook, DO: Hello. This is Jay Shubrook, DO, family physician and diabetologist at Touro University in California. In this continuation of our series on practical use of insulin in primary care, I am happy to welcome my colleague, Kim Pfotenhauer, DO, assistant professor in the Primary Care Department at Touro University, California. Thank you for joining us today.

Kim M. Pfotenhauer, DO: Hello, Jay. Thank you for having me.

Dr Shubrook: Writing a prescription for insulin is, in many ways, much harder than writing a prescription for a tablet or a pill. In fact, pharmacists tell us all the time that insulin prescriptions are one of the most common prescriptions sent back because of errors in how they are written, including being written incompletely.

I would like to talk a little bit about best practices in prescription writing for insulin. When you are writing a prescription for insulin, how do you start? What do you consider?

Dr Pfotenhauer: One of the first things that you have to consider after picking an insulin is what the dose of the insulin is going to be.[1] You have to think about several things. You have to think about the concentration of the insulin that you are using and whether it is dosed in a pen or a vial. For instance, if a patient is taking 10 U in the evening, we know that pens contain 100 U/mL, and there are 3 mL in each pen. If your patient is using 10 U in the evening, the monthly dose is calculated at about 300 U, which would be 1 pen for the month. Similarly, for vials, we could do the same thing, but vials have 10 mL instead of 3 mL; we want to calculate that dose either by 1 month or by 3 months. Just getting used to and getting more comfortable with doing that math is really important as physicians.

Dr Shubrook: So first you pick an insulin, then you pick a pen or vial, and then you pick the dose to know how much you will need. What other things need to be considered for that prescription?

Dr Pfotenhauer: You need to include several things, including the concentration of the insulin, the dose the patient is going to take, and how the patient is going to take it—for example, inject subcutaneously. It is also important to include the diagnosis on the script for insurance purposes.

Dr Shubrook: Really good point. The insurance company will want to know why the person is taking it. How about the time of the day; do you include that in your prescription?

Dr Pfotenhauer: Absolutely. Most long-acting insulin is dosed in the evening, but it can also be dosed in the morning. You want to include that it is dosed just once a day.

Dr Shubrook: That is a really important point because some insulin may be taken more than once a day.

Dr Pfotenhauer: Correct. If you are dosing the insulin at more than once a day, then you have to again do some math and calculate the total daily dose and how that daily dose will translate into pens or vials.

Dr Shubrook: Do you indicate pens and/or vials as part of your prescription?

Dr Pfotenhauer: Absolutely. The pharmacist will need to know what insulin to fill. I will put the concentration of the dose and then the number of pens or vials to be dispensed.[2]

Dr Shubrook: We have to think about a lot of things. We need to include a diagnosis, the daily insulin dose, the time for administration, whether vials or pens should be dispensed, and how many vials or pens we are writing for.

Dr Pfotenhauer: Correct. As you do it more often, it becomes a little bit easier knowing that there are 300 U per pen, so you can calculate a monthly dose easily, and five pens per box. You can also write in the number of boxes vs the number of total insulin units.

Dr Shubrook: I think that electronic medical records have really helped with that. So a short cut I use is: Every 30 U per day of insulin is equal to 1 vial per month. A daily dose of 45 U translates to about one box of five pens. I will very quickly add up my vials or pens based upon those numbers. The other thing is that pens and vials come with different supplies, and we have to write for these needed supplies when we prescribe insulin. Tell me a little bit more about what else we have to write for.

Other Considerations in Prescribing: All of the Other Stuff

Dr Pfotenhauer: Other things we want to definitely include would be a glucometer and test strips. We want patients to be able to check their blood sugars before they take their insulin if the insulin is short-acting or, also, if they are feeling hypoglycemic. Most insurance companies will also cover lancets and alcohol prep pads.

If writing for pens, they will need a specific pen needle. If writing for vials, the specific insulin syringes will also need to be prescribed. Insulin syringes come in different sizes—30, 50, or 100 U. We also have to think about what the patient is going to do with the sharps (needles and lancets) afterwards. Some insurance companies will cover a sharps container, and you can write for that. If they are not able to get a sharps container that is covered by insurance, there are other things patients can use, including an over-the-counter sharps container or something around the house such as an empty detergent container, coffee can, or milk jug.

Dr Shubrook: You talked earlier about the test strips being so important; people should always check their blood sugar before they take an injection of insulin. I like you matching the strips up with the insulin dosing.

Dr Pfotenhauer: The other thing that is important when you are writing scripts for all of the other supplies is to not just write "use as directed." That will often result in the prescription being sent back to you. Instead, be very specific about how often you want the patient to test their blood sugar. For test strips, you can say test up to three times a day or if symptomatic, which gives the patient a little bit of leeway, and the patient may receive extra test strips for the month.

Dr Shubrook: Good point. The last question I have for you is about writing for mealtime insulin. The patient may have a different insulin dose at each meal, and sometimes a dose correction may be needed. How do I indicate that on the script?

Dr Pfotenhauer: It is important to actually write this information on the script. You write down the patient's base dose, whatever that may be. Then you can either write up the correction scale, or you can write, "increase 2 U for every 50 mg/dL [in serum glucose concentration] above 150 mg/dL up to 18 U [of insulin]," for example. It is really important to include the maximum quantity of units that you want the patient to take with every meal and then use that as your calculation dose for the day. For example, if your maximum dose is 20 U per meal, three times a day, you want to give the patient enough insulin so that the patient has 60 U per day for the month.

Dr Shubrook: You have hit so many important points today. To review, when writing for insulin, choose between vials and pens. If using vials, write for syringes at the right size to match the prescribed dose. If writing for insulin pens, prescribe the pen needles. For any of these prescriptions, add all of the necessary supplies, include the diagnosis, and indicate that the patient is taking insulin so that the supplies will be covered by the insurance company. This is such an important topic for primary care providers and chock full of important details. Thank you so much today for your time and your expertise.

Dr Pfotenhauer: Thank you.


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