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Insulin lispro: 7 things you should know

Medically reviewed by Carmen Fookes, BPharm. Last updated on Oct 1, 2021.

1. How it works

  • Insulin lispro is a fast-acting insulin that may be given to improve blood sugar control in adults and children over the age of three with diabetes.
  • Insulin lispro is an analog insulin that is a genetically modified human insulin. Human insulin is made up of a linked A and B polypeptide chains and insulin lispro is made by switching the sequence of two beta-chain amino acids: the proline at B-28 is switched with the lysine at B-29. This results in more rapid dissolution of the insulin to a dimer and then to a monomer which means it is absorbed more rapidly after subcutaneous injection and lasts for less than five hours.
  • The primary activity of insulin, which includes insulin lispro, is to allow cells throughout the body to uptake glucose (sugar) and convert it into a form that can be used by these cells for energy.

2. Upsides

  • May be used to treat type 2 diabetes in adults or type 1 diabetes in adults and children over the age of three, (Admelog and Humalog brands). Lyumjev is only approved for adults over the age of 18.
  • May be used to treat mild-to-moderate diabetic ketoacidosis because it is a rapid-acting insulin (off-label use).
  • May also be used to treat gestational diabetes when nutrition and exercise have not been effective.
  • Insulin lispro does not pass into breast milk and will not affect a nursing infant.
  • Absorbed rapidly after subcutaneous (under the skin) injection, which means it can be given closer to meal times.
  • Insulin lispro is a human insulin analog so it is less likely than regular insulins to cause hypoglycemia.
  • Starts to work 15 minutes after injection, peaks in about one hour, and keeps working for two to four hours.
  • Several different brands are available. Admelog and Humalog are rapid-acting insulins in a conventional formulation and Lyumjev is an ultra-rapid formulation of insulin lispro. These brands differ in their onset of action and administration instructions.
  • Insulin lispro is available in prefilled pens, cartridges, and vials.
  • Less expensive authorized generic versions of insulin lispro are available.

3. Downsides

If you are between the ages of 18 and 60, take no other medication or have no other medical conditions, side effects you are more likely to experience include:

  • Low blood sugar levels (hypoglycemia) are the most common side effect of all insulins, including insulin lispro. The risk of hypoglycemia increases with tighter blood sugar controls, changes in meal patterns, with certain coadministered medications, and changes in physical activity levels. People with liver or kidney disease may be at a higher risk of hypoglycemia.
  • All insulins can cause potassium levels to go low (this is called hypokalemia). Insulin may also cause sodium retention, weight gain, fluid retention and swelling, itching, redness, or lumps around the injection site.
  • The dosage of insulin lispro needs to be tailored to each individual. Requirements can vary dramatically between people.
  • Insulin lispro must be given with an intermediate or long-acting insulin (as a multiple daily injection regimen) or via a continuous subcutaneous infusion device (only Humalog U-100 and Admelog U-100 can be given via an infusion device.)
  • Not to be used to treat diabetes type 2 in children of any age.
  • Cannot be given orally. Must be given subcutaneously (under the skin), by infusion, or, in certain circumstances, intravenously.
  • Use of any insulin, such as insulin lispro, in conjunction with pioglitazone or rosiglitazone, may increase your risk of serious heart problems.
  • The excretion of insulin may be reduced in people with kidney disease (which may extend the length of time insulin lispro works for).
  • Studies that investigated the use of insulin, such as insulin lispro during pregnancy, have not identified a clear association with insulin and adverse developmental outcomes. There are risks to the mother and fetus associated with poorly controlled diabetes in pregnancy such as diabetic ketoacidosis, preeclampsia, spontaneous abortions, preterm delivery, and delivery complications. The risk of major birth defects is 6% to 10% in women with pregestational diabetes with an HbA1c >7 and has been reported to be as high as 20% to 25% in women with an HbA1c >10. In general, the benefits of using insulin during pregnancy outweigh the risks.

Note: In general, seniors or children, people with certain medical conditions (such as liver or kidney problems, heart disease, diabetes, seizures) or people who take other medications are more at risk of developing a wider range of side effects. View complete list of side effects

4. Bottom Line

Insulin lispro is a fast-acting insulin that may be used in conjunction with either an intermediate or long-acting insulin for the treatment of diabetes in adults and type 1 diabetes in children over the age of 3. There are several different brands available and it is available in a cost-saving generic form.

5. Tips

  • Tell your doctor if you have ever had an allergic reaction to any type of insulin before you start using insulin lispro.
  • Children are especially sensitive to the effects of insulin, particularly around puberty.
  • There are so many different types of insulin that medication errors are common. Always check the label on your insulin to make sure it is the brand you have been prescribed and it is the correct strength. Talk to your doctor or pharmacist if you are unsure. Always make sure you dial up the correct dose of insulin lispro for you.
  • The dosage of insulin lispro needs to be individualized. This may take time, so ensure you monitor your blood sugars regularly when titrating the dosage of insulin lispro, and tell your doctor the results.
  • Never share your insulin lispro with other people. Store your insulin lispro as recommended on the label.
  • Inject your insulin exactly as directed by your doctor. Take all other medications as prescribed.
  • Your insulin requirements may change if you become unwell, develop an infection, or other medical conditions. Surgery, injury, mental stress, your diet, and how much exercise you do can also affect how much insulin you need. Puberty, pregnancy, and menopause can also affect insulin requirements. Conditions that delay food absorption or stomach emptying can slow down the time it takes to break down and absorb food which can change how much insulin you need.
  • Be alert for symptoms of hypoglycemia which may include a headache, sweating, trembling, anxiety, confusion, irritability, rapid breathing, or a fast heartbeat. People with hypoglycemia may also faint and severe hypoglycemia that is left untreated may be fatal. Tell your family, friends, and caregivers to give you some fast-acting sugar (such as some jellybeans, fruit juice, or honey) if they notice you have symptoms of hypoglycemia and then follow it up with a more substantial meal or glucagon injection if you are unconscious.
  • Insulin is easily broken down by extreme temperatures, which means you need to be careful if you live in a part of the U.S. that gets very hot in summer, or very cold in winter.
  • Store unopen insulin lispro in the refrigerator between 36-46 degrees Fahrenheit. Insulin lispro that has been opened may be kept at room temperature (59 to 86 degrees Fahrenheit [15-30 degrees Celcius]) for up to 28 days. After dilution, storage times vary depending on the brand (check the manufacturer's product instructions).
  • If you are going out in the sun, always use an insulated bag protected by a cool pack to ensure your insulin lispro doesn't heat up; but avoid freezing it. During cold weather, keep your insulin lispro close to your skin so your body heat keeps it at a more even temperature. Discard any insulin lispro that you think may have inadvertently got too hot or too cold. The expiry date on insulin lispro applies to unopened, refrigerated insulin.
  • If you become pregnant while taking insulin lispro, tell your doctor immediately. Controlling diabetes during pregnancy is very important and high blood sugar levels can be detrimental both to you and your developing baby.

6. Response and effectiveness

  • Time to onset, peak effect, and duration of action varies depending on the brand. In general, insulin lispro is a fast-acting insulin that starts to work 15 minutes after injection, peaks in about one hour, and keeps working for two to four hours.
  • Admelog: Onset 31 minutes; time to peak 50 minutes; duration of action 6.9 hours. Humalog: Onset 31 minutes; time to peak 50 minutes, duration of action 5.7 to 6.6 hours. Lyumjev: Onset 15 to 17 minutes, time to peak 57 minutes; duration of action 4.6 to 7.3 hours. Note all these times are averages and can vary depending on whether a person has type 1 or type 2 diabetes or the source of information.
  • The recommended initial total daily dose is 0.4 to 0.5 units/kg/day in divided doses. Conservative initial dosages are 0.2 to 0.4 units/kg/day which may be considered to avoid the potential for hypoglycemia. Higher initial dosages may be required in patients who are obese, sedentary, or who present with diabetic ketoacidosis. Generally, 40% to 50% of the total daily dose of insulin is given as basal insulin in the form of an intermediate or long-acting insulin, then the rest is divided and administered around mealtimes as a fast or rapid-acting insulin.
  • Although one unit of insulin lispro has the same glucose-lowering effect as one unit of regular insulin, it has a faster rate of absorption after injection, an earlier and greater insulin peak, a more rapid post-peak decrease. Insulin lispro only needs to be given 15 minutes before or immediately after a meal whereas regular insulin needs to be administered 30 minutes before a meal. This is an important safety consideration because if insulin is administered to a diabetic, and then they forget to eat or their meal is delayed, they could develop hypoglycemia.
  • Because insulin lispro has a shorter duration of action than regular insulin, this reduces the risk of low blood sugars immediately following a meal (postprandial hypoglycemia). Insulin analogs are also less likely to cause hypoglycemia (low blood sugar levels) in general.
  • American College of Obstetricians and Gynecologists (ACOG) and The Endocrine Society recommend either insulin lispro or insulin aspart instead of regular insulin for the treatment of gestational diabetes.

7. Interactions

Medicines that interact with insulin lispro may either decrease its effect, affect how long it works for, increase side effects, or have less of an effect when taken with insulin lispro. An interaction between two medications does not always mean that you must stop taking one of the medications; however, sometimes it does. Speak to your doctor about how drug interactions should be managed.

Common medications that may interact with insulin lispro include:

  • antibiotics, such as doxycycline and minocycline
  • antidepressants such as SSRIs (eg, fluoxetine, sertraline), monoamine oxidase inhibitors (MAOI) such as selegiline, isocarboxazid, and phenelzine
  • antiepileptics, such as fosphenytoin and phenytoin
  • antipsychotics, such as aripiprazole, chlorpromazine
  • antivirals such as amprenavir, atazanavir, and fosamprenavir
  • aspirin
  • beta-blockers, such as acebutolol, atenolol, or timolol
  • cyclosporine
  • diuretics, such as furosemide, chlorthalidone, or hydrochlorothiazide
  • fluoroquinolone antibiotics, such as ciprofloxacin or norfloxacin
  • gemfibrozil
  • heart medications such as captopril, candesartan, or clonidine
  • hormones, such as estradiol, estrone, and norethindrone
  • lithium
  • niacin
  • pentamidine
  • salmeterol
  • steroids, such as cortisone, dexamethasone, fludrocortisone, or prednisone
  • sucralfate
  • tacrolimus or pimecrolimus
  • topiramate
  • turmeric
  • aloe vera
  • other insulins
  • other medications that affect blood sugar levels or are used for diabetes, such as chlorpropamide, glimepiride, or glipizide.

Alcohol may also interact with insulin lispro by blocking the production of glucose by the liver, causing hypoglycemia.

Note that this list is not all-inclusive and includes only common medications that may interact with insulin lispro. You should refer to the prescribing information for insulin lispro for a complete list of interactions.


Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use Insulin lispro only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Copyright 1996-2022 Revision date: September 30, 2021.