Part 1: Insulin - What you need to know
Updated: Mar 4
In the past 18 months, two new insulins were added to Australia’s Pharmaceutical Benefits Scheme, Fiasp and Toujeo. If you’re thinking about using one of these new insulins – or any new insulin - it’s vital you know how it works: when it starts working, when it peaks and how long it lasts for. In Part 1 of this two-part Clinic Chat series, we’ll inject some meaning into ultra rapid-, rapid- and short-acting insulins.
Rapid-acting insulins: NovoRapid, Humalog and Apidra For people on needles, rapid-acting insulin covers the carbohydrates in food and corrects high blood glucose levels. People on pumps exclusively use rapid-acting insulin, as both their basal (background) insulin and bolus (meal and correction) insulin. The amount of rapid insulin needed for a meal or correction is determined by two formulae: the individual’s insulin-to-carbohydrate ratio (ICR), which is the number of grams of carbohydrate covered by 1 unit of rapid-acting insulin, and their insulin sensitivity factor (ISF), which is the number of mmol that 1 unit of insulin will reduce blood glucose by. You can learn more about calculating ICR and ISF in the Family Centre’s online carbohydrate counting course, Cyber Carbs. Rapid-acting insulin can be used by people of all ages. It starts working about 15-20 minutes after it is injected, so it is sometimes advised to inject rapid-acting insulin 15-20 minutes before a meal (a ‘pre-bolus’), rather than just before eating. Ultra-rapid acting insulin - Fiasp Fiasp (even the name sounds fast!) is the latest evolution in ‘ultra-rapid’ mealtime/bolus insulin. Fiasp can be taken immediately before a meal, and even up to 20 minutes after you’ve started eating. Fiasp is the same insulin as the rapid-acting insulin NovoRapid, with the addition of two ingredients, niacinimide (Vitamin B3) and the amino acid L-arginine, which increase the speed at which Fiasp is absorbed into the blood. The diagram below shows how Fiasp compares to NovoRapid in terms of onset, peak and duration. Fiasp is more active in the first hour than NovoRapid, which is useful if you’re eating carbohydrates with a high glycaemic index that will spike your glucose level quickly. Like NovoRapid, Fiasp lasts for 4-5 hours, however, there will be slightly less active Fiasp left during the final 3-5 hours compared to NovoRapid. In Australia, Fiasp is approved for use in people with type 1 diabetes over the age of 18 for both injections and pumps. Clinical data are now available for paediatric use and Novo Nordisk, who make Fiasp, may seek TGA approval for Fiasp to be used by children and adolescents. There is currently not enough trial data to recommend Fiasp to women who are pregnant. Patients have reported to the Family Centre that using Fiasp in their insulin pumps has left them with unexplained high blood glucose after around 48 hours. You can read more about Fiasp and pumps from the International Diabetes Federation’s ‘Diabetes Voice’ here. Patients who inject, rather than a pump, Fiasp seem to have fewer problems. If you’re interested to try Fiasp, you’ll need a script from your endo or GP, and support from your diabetes educator to transition onto the new insulin. Remember – Fiasp acts faster than rapid-acting insulin, so be mindful of potential hypoglycaemia risks, especially if you’re using it to cover a meal that is high in fat or protein, which will be absorbed slowly.
Short-acting insulin Short-acting insulins, such as Humulin R and ActRapid (also known as 'regular' or 'human' insulins) are older insulins that are also used to cover carbohydrates and correct high blood glucose levels. However, they take 30 minutes to start working, so they’re not as good as rapid-acting insulins for carbohydrate-based meals. Short-acting insulin is popular with people who utilize a reduced-carbohydrate approach to type 1 management. Because it peaks later than rapid-acting insulin, low-carbers use short-acting to cover the delayed increase in blood glucose they see from the digestion of protein. (New to protein bolusing? Learn about the impact of protein on your blood glucose in Cyber Carbs). Short-acting may also be useful to cover the delayed absorption of carbohydrates from meals that are high in fat. Short-acting insulin can last up to eight hours in the body, which is important to remember, especially if you’re considering activity with short-acting onboard. Short-acting insulin can be used by people of all ages, but cannot be used in pumps. Do you want to talk through your insulin regimen, and discuss the options you have? Contact the Family Centre’s diabetes educators, Amy and Inger. Stay tuned for next month, where we’ll talk about intermediate-, long- and ultra-long-acting insulins.