A rapid-acting (mealtime) insulin
Insulin lispro
A rapid-acting (mealtime) insulin injected around eating to cover the rise in blood glucose after food.
What is Insulin lispro?
Insulin lispro is a rapid-acting insulin used at mealtimes to cover the rise in blood glucose that food causes. It starts working quickly and lasts only a few hours, so it is usually injected just before, or sometimes just after, eating. In type 1 diabetes it is used alongside a separate long-acting background insulin. Because it lowers blood glucose, the main risk is a hypo, so match it to your food and learn the warning signs of a low. Always rotate injection sites and never share a pen or needles.
Education and reference only. This is a plain-language guide to Insulin lispro — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Insulin lispro is a fast-acting (mealtime, or bolus) insulin analogue used in type 1 and type 2 diabetes. It was the first of the rapid-acting analogues and works soon after injection, lasting only a few hours to match the glucose rise after eating. It is the insulin taken with meals, while a separate long-acting insulin covers the background needs. It comes in prefilled pens, cartridges and vials, and a faster version is designed to be taken right at the start of a meal.
How it works
After you eat, blood glucose rises as food is digested. Insulin lispro is absorbed quickly under the skin and acts over a short window, helping move that glucose into the cells before it climbs too high. Because it works fast and fades quickly, it is timed around meals and snacks. In type 1 diabetes it is paired with a long-acting background insulin so that both mealtime peaks and the body's steady needs are covered.
Company & origin
Originated / developed by: Eli Lilly (Humalog, Lyumjev); Sanofi (Admelog).
The first rapid-acting insulin analogue, developed by Eli Lilly in the 1990s, with a faster-acting version (Lyumjev) introduced more recently for mealtime use in the UK.
What it treats
Conditions Insulin lispro is used for
Practical use
How to take Insulin lispro
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Inject under the skin just before a meal, or at the start of eating for the faster version, into the tummy, thigh or upper arm.
- Match the timing to your food, and do not inject it without eating unless your diabetes team has advised this.
- Rotate your injection site within an area each time to avoid lumpy or hardened skin that changes absorption.
- Use a new needle each time and never share a pen or needle with anyone else.
- Carry fast-acting sugar such as glucose tablets and learn the warning signs of a hypo.
- On sick days keep checking your blood glucose and follow your sick-day plan rather than stopping insulin.
Weighing it up
Advantages & disadvantages of Insulin lispro
Advantages
- Works quickly and fades within a few hours, closely matching the glucose rise from a meal.
- Can be injected right before, or with the faster version at the start of, eating for flexibility around food.
- Long-established and well understood, available in pens, cartridges and vials.
Disadvantages
- Like all insulin it can cause hypoglycaemia, especially if a meal is delayed, missed or smaller than planned.
- Its short action means several injections a day are usually needed alongside a separate background insulin.
- Getting the timing right relative to food takes some learning and attention.
Practical use
Good to know
Lispro is a mealtime insulin, so its timing is tied to eating: it is usually injected just before a meal, with the faster version taken right at the start of or shortly after eating. If you take it but do not eat, your blood glucose can drop too low, so do not inject it without food unless advised. The most important safety point is hypoglycaemia: warning signs include shakiness, sweating, hunger, a fast heartbeat and confusion, and a hypo is treated with fast-acting sugar then a snack. Inject under the skin, rotate sites to avoid lumpy skin that changes absorption, and never share a pen or needle. On sick days, keep monitoring and follow your sick-day plan rather than stopping insulin, as illness often raises glucose.
Who should not take it / use with caution
- It must not be used during an episode of low blood glucose (hypoglycaemia).
- People with a known allergy to insulin lispro or its ingredients should not use it.
- It should not be injected without a planned meal unless a clinician has specifically advised this.
Monitoring
- Regular blood glucose checks, especially around meals, and HbA1c over time.
- Reviewing injection sites for lumps or hardened skin that can affect absorption.
- Watching the pattern of hypos in relation to meals and activity to fine-tune treatment.
Side effects
- Hypoglycaemia (low blood glucose) is the most important side effect, with shakiness, sweating, hunger and confusion.
- Redness, itching or lumpy, hardened skin at injection sites if sites are not rotated.
- Weight gain and, rarely, allergic reactions.
Key interactions
- Other glucose-lowering medicines, alcohol and some painkillers can increase the risk of a hypo.
- Steroids, some diuretics and certain other medicines can raise blood glucose and reduce insulin's effect.
- Beta-blockers can mask the warning signs of a hypo, so extra glucose monitoring may be needed.
Available as: Solution for injection under the skin, in prefilled pens, cartridges and vials.
Answers
Insulin lispro: frequently asked questions
When do I inject insulin lispro?
It is usually injected just before a meal; the faster version can be taken at the start of, or shortly after, eating. It is a mealtime insulin matched to your food.
Is lispro the same as aspart?
Both are rapid-acting mealtime insulins that work in much the same way; your team chooses one based on what suits you and what is available.
What if I inject it and then skip the meal?
Your blood glucose could fall too low, so do not take mealtime insulin without food unless your team has specifically advised it.
How do I treat a hypo?
Take fast-acting sugar such as glucose tablets or a sugary drink straight away, then a snack, and always carry sugar with you.
Can I share my pen if I change the needle?
No. Pens and needles must never be shared, even with a new needle, because of the risk of passing on infection.
The wider class
About Insulin
Insulin lispro belongs to the insulin class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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