This is Dr. K., your online pharmacist, here to talk to you some more about insulin. I had to start with a little pharmacy joke to introduce this post – yes, we pharmacists do have a sense of humor!
If you missed it, my previous post about insulin can be found here. We’ve already discussed how your body makes its own insulin and how that lowers your blood sugars. We’ve talked about various medications that affect how your body uses and produces insulin. But today, we are going to look at insulin as a medication, a helpful drug that your doctor might choose to use in your fight against diabetes. Today I will be discussing the different types of insulin that we use, and important tools that you should have for your doctor when sitting down to talk about insulin for the first time.
Insulin is a chemical that is usually produced by our pancreas to help keep our blood sugar at a healthy level. If you are a diabetic, your body might not produce enough insulin, or might not be able to use insulin correctly. So sometimes we have to give you extra insulin, via an injection into your fat cells, to keep your blood sugars on track. When used at low levels, insulin causes your liver to stop making extra glucose (remember, glucose is sugar and we don’t want your body to make more than it needs). As we increase the amount of insulin we give you, the insulin actually helps your cells “take up” glucose from the blood (we want glucose in your cells and not in your blood). Just like with the other medications I’ve talked about, insulin works in a number of different ways to lower your blood sugar – it “attacks” diabetes from all sides!
Not all insulin is the same. We categorize insulin based on how fast it takes it to lower your blood sugar and how long it continues to keep your blood sugar lowered. Some insulin works very quickly – within 15 minutes – but only lasts for about 3 hours. Other insulin can take up to 1 to 2 hours to work, but can continue to work for anywhere from 12 to 24 hours. These numbers are important because they affect when you take your insulin shots, how many times a day you will have to inject yourself, and which insulin we will use if your blood sugars are high at a certain time of the day.
But before we get into that, let’s break down the different “classes” of insulin. You probably thought that we were done talking about “classes” of medications, didn’t you? Well no such luck, my friends. I promise to make things easy!
Rapid-Acting Insulin – This is the group of insulin that works the quickest. After you inject these, they take approximately 15 minutes to start working, reaching their “peak” after 30 to 60 minutes. Rapid acting insulin works in the body for about three hours. Since they work so quickly, this type of insulin is perfect for injecting before you eat in order to cover the current meal. Humalog, Novolog, and Apidra are all brand names of rapid acting insulin.
Short-Acting Insulin – There is only one insulin in this heading – regular insulin, otherwise known as Novolin R or Humulin R. It does not qualify as rapid acting, because regular insulin takes about 30 minutes to first start working, and doesn’t reach its peak until about 2 to 5 hours after injection. Regular insulin works in the body for about 5-8 hours.
Intermediate-Acting Insulin – The only insulin in the intermediate-acting class is NPH insulin, otherwise known as Novolin N or Humulin N. Intermediate-acting insulin takes about 1 to 2 hours to start to work in the body, and about 4 to 6 hours to reach its peak. It will continue to work to lower your blood sugars for about 8 to 12 hours.
Long-Acting Insulin – There are two different long-acting forms of insulin, and I find them easy to remember because they both start with an “L” like “long-acting”: Lantus and Levemir. These two also take about 1 to 2 hours to start working, just like NPH insulin. But, long-acting insulin forms do not reach a “peak” – their levels are very stable and flat while they are working in the body. And the best thing – Levemir has its effects for 12 to 20 hours, and Lantus can work for up to 24 hours after injection! This means that one shot could, potentially, last the entire day.
Mixed Insulin – Just for completeness, I am going to mention that there are mixed forms of insulin as well. Insulin N and R can come pre-mixed – known as 70/30 or 50/50. We also have Novolog Mix 70/30 and Humalog Mix 70/30. We don’t generally see these used as much, but once in awhile I will have a patient on one of them.
So now that we know this, what does it all mean? Well, the first thing I need to tell you is that every person is different. Yes, I know I’m “Captain Obvious” today! But what I really want to point out is that every person is going to have a different regimen of injecting insulin. Just like we don’t use metformin on every patient with diabetes, we don’t use the same type of insulin for every patient. There are so many things to keep in mind when choosing, with your doctor, which insulin is the right one for you. And this is where I want to be clear – your doctor needs to ultimately be the one to select your insulin and prescribe it, but it is up to you to give your doctor the proper information to help them to decide which insulin to use.
Here on the blog, Phil has provided you with the first tool that your doctor needs to see – your food diary. If you don’t have one, start one, especially if you were just diagnosed or you have been having trouble with low or high blood sugars. This tool lets your doctor know two things that are essential for choosing the right insulin for you: when your sugars are highest/lowest, and how food affects your numbers. As you just saw, each type of insulin starts working at a different time, so now it’s just a matter of working the numbers. Our goal is to keep your blood sugar levels as stable and flat as we can, with no “peaks” or “valleys.”
Let’s take an example: suppose your blood sugar is higher than we want it to be when you check your blood sugar in the morning before eating breakfast. Imagine that we’ve determined that these levels are not from the dawn phenomenon that we’ve talked about before. These levels are high because of the bedtime snack that you had the night before, which your doctor will be able to see from the food diary. Your doctor would then choose to have you do an injection of intermediate or long-acting insulin before dinner or before bedtime to help bring down your levels in the morning – remember, these types of insulin can work for 12 hours in the body, which will cover those early morning spikes.
Another example: suppose your bedtime blood sugar reading is the one that is high. By looking at your food diary, your doctor would be able to see when you’d last eaten and where your normal levels are. In this case, we would have you inject a short-acting insulin (regular insulin) before you eat your evening meal. Without the numbers and eating times from your food diary, your doctor will have a much harder time choosing which insulin is right for you – with insulin, timing is everything.
The other thing to consider with choosing an insulin is how the injections will fit into your daily life. Remember, you have diabetes, but it does not define your life. Will you be able to inject insulin four or five times daily? Some people have no choice, because of how their body works. But this is something to discuss with your doctor – would a long-acting insulin that only has to be injected once daily be the right fit for you? Also, timing your injections with your meals is very important. If you inject insulin and accidentally skip or postpone a meal for too long, your blood sugar levels will drop dangerously low – a very serious and life-threatening emergency. Rapid-acting insulin is great because it starts working within 15 minutes, but this also means that you must eat within 15 minutes of injecting. With short-acting insulin you have to eat within 30 minutes. For people with ever-changing schedules and no set times for meals, these are important things to consider. Be upfront and honest with your doctor about your eating habits so that we choose the right insulin for you.
Next time I will discuss tips for injecting insulin and how to get the most out of the insulin that you are injecting.
As a disclaimer, I am your “virtual” pharmacist, here to provide you with information and answers to questions. However, I am not your local pharmacist and could, in no way, be aware of your specific medical needs. Remember to always check with your medical provider and pharmacist before stopping or starting any new medications. My posts are based on general pharmacy principles and should not considered as your “first opinion” when it comes to your health. Please consult with your doctor and pharmacist about anything regarding your health.