Dosing Insulin: The Most Important Thing Is the Education

Jay H. Shubrook, DO; Gerard Victor A. Sebastian, MD


August 29, 2017

Jay H. Shubrook, DO: Hi. I'm Jay Shubrook, DO, professor and diabetologist at Touro University. We're at the 77th Annual American Diabetes Association Scientific Sessions. I'm here with one of my colleagues to continue the program on practical use of insulin in primary care.

Today I'm talking with Gerard Sebastian, MD. He's a family physician and fellowship-trained diabetologist, and his practice in Longview, Washington, combines both primary care and diabetes specialty care. Welcome to the program.

Gerard Victor A. Sebastian, MD: Thank you.

Timing Basal Insulins

Dr Sebastian: Today I'd like to talk about the timing of insulin dosing. There are so many insulins and they all have different profiles; timing can be lost sometimes. Let's start with basal insulin. For the basal insulins, when do you like to dose it and what instructions do you give?

Dr Sebastian: Every time I see new patients or new consults especially, I always explain to them the mechanism of action for each insulin and the best time to take these insulins. With the basal insulins, we all know that this insulin lasts for 24 hours. This is particularly true with Lantus® [insulin glargine injection] and the newest and longest-acting basal insulin product, Tresiba® [insulin degludec injection]. I always ask patients what time of day is convenient for them to take this medication, because it's better for patients to take them at least once a day and at the most convenient time so that they won't forget. Consistency is important for patients with this medication.

Dr Sebastian: So, the time of day doesn't matter as long as it's a time that's convenient for them and the time is relatively consistent. That's an important point. If I'm going to take it in the morning, it's got to be consistently in the morning.

Dr Sebastian: Yes.

Dr Sebastian: Some people take basal insulin twice a day. When would you do that?

Dr Sebastian: Typically, I consider it if a patient's taking large doses of insulin—more than 60 or 80 units. If they're using insulin pens, some of these pens contain a maximum of 60 units. The newest pens now on the market can be up to 80 units. For patients taking 80-plus units of basal insulin, I usually recommend splitting the dose.

Dr Sebastian: Particularly if a patient is exceeding the dose of the pen, that's a great time to split the dose. That is mostly because of the mechanics, as that patient is going to have to take two shots anyway. That's helpful, and I think that's important for our patients.

Timing Mealtime Insulins

Dr Sebastian: What about mealtime insulin? We have many choices, and while we do give instructions to our patients, they may follow their own path when they take insulin. How do you introduce the concept of timing of the dose for mealtime insulin?

Dr Sebastian: This is the most common insulin that patients use incorrectly. Some of them take it with meals, some take it after meals, which doesn't really work. Patients think that most rapid insulin or short-acting insulin has the same actions. For patients taking regular insulin, which we all know hits the blood about 30 minutes after an injection, I recommend taking it 20-30 minutes before each meal. For newer insulins or the analog insulins, especially for patients who are having some memory issues, I tell them to take it right before they eat.

Dr Sebastian: That becomes complicated because we use all of those insulins. Do you have patient handouts? How do you specify timing to the patient and how do you reinforce it?

Dr Sebastian: I discuss this with patients at length at every visit so that they get this proper time correctly. If they need more time, we have handouts that we give them. I also have diabetes educators in our clinic to give more information to our patients.

Dr Sebastian: Having educators is so important. It really makes a difference. I have patients who say, "I'm not sure how much I'm going to eat at a particular meal. I'm nervous about taking my insulin before the meal. Once I eat, I know what I ate." What do you tell them?

Dr Sebastian: In this instance, we usually try to adjust the insulin. To make it simple for the patients, I always advise them that if they don't have that appetite at that moment, if they think that they're going to anticipate just eating half of their usual meal, I would advise them to take just 50% of their usual dose to prevent hypoglycemia.

Dr Sebastian: That's a practical answer. If they're not sure they're going to eat, they can make the insulin match their food. Of course, most people who take mealtime insulin, at least in our practices, take both insulin for their food and insulin to treat their high sugars. I see patients who will take their insulin for their meal beforehand and then the correction afterwards. What do you recommend?

Dr Sebastian: That's not a proper way to do that. The correction should be included with the meal or the insulin coverage for the carbohydrates given before the meal. I always emphasize that they need to add the corrections to the base insulin for the meal. If the patient says that they will not eat at that mealtime, I always tell them that they can take just the correction, without the base insulin, in order to correct if their blood sugar is high.

Dr Sebastian: That is such an important thing. At every mealtime, it sounds like you want your patients who have mealtime insulin to check their glucose. Either way, they should be considering insulin. If they're going to eat, they'll have a dose that goes with their meal. If they're not going to eat, they still need to consider the correction dose.

Dr Sebastian: Yes, that's correct.

Dr Sebastian: What about the math? That math can be quite hard for patients. Do you have any advice about how to help people when they're timing their dose and then giving the right dose?

Dr Sebastian: At every visit, I always calculate the dose for them. To calculate a correction dose for patients with type 2 diabetes, I use 1500 divided by the patient's total daily insulin dose to estimate the amount of insulin required [see "The 1500 Rule" below]. For type 1, I use 1800 divided by their total daily insulin dose. If the patient is capable of doing the carb ratio, I also calculate that. I like the carb ratio compared with a fixed dose of bolus insulin because it matches the amount of insulin to the carb intake, and that decreases the risk for hypoglycemia.

Calculating Insulin Sensitivity: The 1500 Rule [1]

Divide 1500 by the total daily dose of regular insulin, in units. For example, an individual with a total daily dose of 30 units of regular insulin has an insulin sensitivity factor of 50 (1500 ÷ 30). By this calculation, one unit of regular insulin would be estimated to lower this person's blood glucose by 50 mg/dL.

Dr Sebastian: It sounds like you do a fair amount of patient education to make sure that they get the right dose.

Dr Sebastian: Yes.

Educating Patients: Getting the Right Dose at the Right Time

Dr Sebastian: When you look at insulins, either regular insulin or the rapid-acting analogs, how do patients know whether it's working? How do you help them to define whether they got the right dose at the right time? Do you ever see how much their glucose checks?

Dr Sebastian: Yes. I always advise them, especially if we're starting a new dose, to check their blood sugar 2 hours after meals. The goal we set is based on the guideline, which states that postprandial glucose should be less than 180 mg/dL.[2] I also ask them to check it before the next meal, especially if their meal times are about 4 hours apart. The blood sugar should be less than 150 mg/dL. By dose numbers, that would give us an idea that we got the right dose of bolus insulin.

Dr Sebastian: They have to check a glucose level both times to know. To summarize, today you talked about the importance of basal insulin, which can be taken anytime, although patients should pick a stable time of the day and take it regularly at that time. With mealtime insulin, recognizing the kinetics of the insulin, we should make sure that patients take it before the meal. But what if the patient forgets? We've all heard patients say, "I was busy today and I had lunch and forgot to take my insulin."

Dr Sebastian: If it is a very rare or occasional event, then just to be safe, I would advise them to just skip that dose and wait for the next meal. If they do check their blood sugar between meals, I advise them to just use their correction without the fixed dose or the carb ratio.

Dr Sebastian: Really important things you shared today. Thanks for coming in.

Dr Sebastian: It was a pleasure to be here. Thank you.


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