If you’ve arrived on this page, you’ve more than likely been searching the internet to figure out what people are talking about when they say the words basal and bolus. The concept of basal and bolus insulin shouldn’t be a mystery, so I’m here to clear it up and give you an idea on what we’re all talking about!
What is Basal Insulin?
Basal insulin is what is known as background or long lasting insulin. A lot of diabetics, both T1 and T2, will take 1 shot of basal insulin a day either in the morning or night. However, not all basal insulins last a full 24 hours so some decide to split their dose into 12 hour intervals. For example, I take my biggest dose at 9pm and then a much smaller dose at 9am for 24 hour coverage.
So I’m sure you’re thinking “well, thanks, but what does basal insulin actually do?”. As I said in the above paragraph, it’s a background insulin. It’s meant to keep blood glucose at a consistent level all day and night, every day and night. It’s not meant to cover any carbs or protein that’s eaten through the day.
Some of the popular basal insulin brands right now are:
- Insulin glargine (Lantus, Basaglar, Toujeo): starts working about 1 to 1.5 hours after injection. The pharma company that makes it claims there is no actual peak and it’s supposed to last 20-24 hours.
- Insulin detemir (Levemir): starts working 1 to 2 hours after injection, peaks in 6-8 hours and is supposed to last up to 24 hours.
- Insulin degludec (Tresiba): starts working 30 minutes to 1.5 hours after injection, not supposed to have any peak, and the claims is that it works for 42 hours.
What is Bolus Insulin?
If basal insulin runs consistently in the background, bolus insulin is what is known as ‘mealtime’ insulin. A lot of people refer to it as rapid acting insulin but not all prescribed mealtime is actually all that rapid. There’s different classifications.
Rapid Acting Insulin:
- Insulin lispro (Humalog, Admelog): starts working 15 to 30 minutes after injection, peaks in 30 to 90 minutes and stays in the system for 3 to 5 hours.
- Insulin aspart (Novolog, Fiasp): starts working 10 to 20 minutes after injection, peaks in 30 to 40 minutes and stays in the system for 3 to 5 hours.
- Insulin glulisine (Apidra): starts working 20 to 30 minutes after injection, peaks in 30 to 90 minutes and stays in the system for 1 to 2.5 hours.
Short Acting Insulin:
- Regular (R) or novolin: starts working 30 minutes to 1 hour after injection, peaks in 2 to 5 hours and stays in the system for 5 to 8 hours.
- Velosulin (used in pumps): starts working 30 to 1 hour after injection, peaks in 1 to 2 hours and stays in the system for 2 to 3 hours.
Intermediate Acting Insulin:
- NPH (N): starts working 1 to 2 hours after injection, peaks in 4 to 12 hours and stays in the system for 18 to 24 hours.
Why Use Basal and Bolus Together?
In a nutshell, it offers flexibility. If you read the book ‘Think Like a Pancreas’, the author describes old insulin therapies where you took a set amount and had to eat around the insulin or a sliding scale. With both basal and bolus, you can control your overnight blood glucose while not having to (in theory) be bound to a certain diet.
Of course, having mealtime insulin doesn’t give anyone the right to eat like crap. Covering carbs doesn’t magically cancel out calories nor does it make postprandial spikes go away if you’re eating a lot of carbs in one sitting.
And if you want even more flexibility, you can consider using a pump (I’m not quite there yet).
To wrap this up, when you think of basal bolus think that one injuection is only once or twice a day and the other is to cover what you eat and make corrections to your raising blood glucose over the day.