The pancreas of a person without diabetes secretes an amount of insulin continuously throughout the day and, additionally, after each meal, a larger amount to metabolise the carbs consumed. These two components are substituted by long-acting or intermediate-acting insulins and fast-acting insulins, respectively. Additionally, there are premixed insulins that include both fast-acting and intermediate-acting insulin in the same device.
Here are the types of insulin that are on the market, as well as factors that can affect their action:
It is known as NPH insulin: it lasts around 10-13 hours, its action peaks between 4-7 hours and becomes active after 1-2 hours. It has a milky appearance. Its activity is very variable from one day to the next, with a risk of hypoglycaemias (low blood sugar) due to its action peak and, so that it covers 24 hours, it must be administered in 2 or 3 daily doses.
Insulin glargine U100 (Lantus®): has a half-life of 20-hours, starts acting in 1-2 hours and does not have a pronounced activity peak, which reduces the risk of hypoglycaemias with regard to NPH insulin. It is normally administered in a single daily dose. Less variability than NPH insulin. Insulin glargine U300 (Toujeo®) is a new version of the U100, with a greater concentration that makes it last longer, with a half-life of 24 hours and less hypoglycaemias with less variability.
Insulin Detemir (Levemir®): has a half-life of 12-16-hours, starts acting in 1-2 hours and does not have a pronounced activity peak, which reduces the risk of hypoglycaemias with regard to NPH insulin. It normally requires being administered twice a day to cover 24 hours. It also shows less variability than NPH insulin.
Insulin Degludec (Tresiba®): has a half-life of more than 24 hours, which ensures daily coverage with a single injection with regard to NPH insulin.
Ultra-fast-acting insulins: we currently have access to Lispro (Humalog®), Aspart (Novorapid®) and Glulisine (Apidra®). All 3 of them have similar characteristics: they become active in 10-15 minutes after the injection, their activity peak is after 30-90 minutes and they last between 3 to 4 hours.
Regular insulin (Actrapid®) is less physiological, that is, it emulates insulin secretion by the pancreas poorly. It becomes active 30-60 minutes after the injection. Its activity peak is after 2-3 hours and lasts 5-7 hours.
Faster Aspart (Fiasp®): it becomes active twice as quickly, which leads to a an earlier drop in glucose compared to Aspart insulin (which allows for better control of glucose after a meal in the first two hours). Its duration is similar and it peaks 1 to 3 hours after being injected. It seems that insulin pump users will probably gain more advantages from this new insulin.
There are several pre-established insulin mixes on the market, akin to fast or regular-acting and intermediate-acting insulin. The disadvantage is that the percentage of each type of insulin is pre-set and the insulins cannot be modified individually.
Factors that modify insulin action
|The following advance the action of insulin:|
|Physical exercise of the area that has been injected.|
|Heat on the injection area.|
|A massage on the area injected with insulin.|
|If the injection is too deep, because the insulin could be injected into the muscle.
|Injection on abdomen and arms.|
|Very small doses.|
|The following delay the action of insulin:|
|Cold on the injection area.|
|If the injection is too superficial.|
|Injection on areas with lipohypertrophy. It does not only delay absorption, but also makes it more erratic and less reliable.
|Injection on buttocks or thighs.|
Written by Dr Cintia González Blanco, Consultant 1 Endocrinology and Nutrition Service at Hospital de Sant Pau, Associate Professor at UAB and member of CIBER-BBN, Coordinator of the 2.0 diabetes group and member of the SED technologies applied to diabetes group; she is part of the editorial committee at SocialDiabetes.