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Humalog: 7 things you should know

Medically reviewed by Carmen Pope, BPharm. Last updated on July 5, 2023.

1. How it works

  • Humalog is a brand (trade) name for insulin lispro which 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.
  • Humalog (insulin lispro) is an analog insulin that is a genetically modified human insulin. Human insulin is made up of 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 a 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 Humalog, 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.
  • Humalog belongs to the class of medicines known as insulins.

2. Upsides

  • Approved to treat type 1 and type 2 diabetes in adults and type 1 diabetes in children over the age of 3 years.
  • Absorbed more rapidly after subcutaneous injection than regular insulin and lasts for less than five hours.
  • Because it is absorbed rapidly Humalog can be given closer to meal times.
  • Starts to work 15 minutes after injection, peaks in about one hour, and keeps working for two to four hours.
  • This means it can be administered 15 minutes before or with a meal. This has safety benefits over regular insulin that needs to be administered 30 minutes before food, especially if a meal is delayed or forgotten because hypoglycemia may result.
  • Humalog has a shorter duration of effect than regular insulin. This means lispro better mimics how insulin is naturally released in people without diabetes and reduces the risk of side effects such as low blood sugar levels (hypoglycemia) following a meal.
  • Has the same glucose-lowering effect as one unit of regular insulin but has an earlier and greater insulin peak and a more rapid post-peak decrease.
  • There are two different types of Humalog: Humalog, a rapid-acting insulin, and Humalog Mix, which is a combination insulin that combines a short-acting insulin with a longer-acting insulin.
  • Humalog Mix is available as Humalog 50:50 which contains 50% insulin lispro protamine and 50% insulin lispro; Humalog 75:25 which contains 75% insulin lispro protamine and 25% insulin lispro.
  • Prefilled pens are available in two different strengths: Humalog U-100 and Humalog U-200. However, no dose conversion is necessary because the dose window of the prefilled pen shows the number of insulin units to be delivered. Do not mix the prefilled pens with other insulins.
  • Does not pass into breast milk and will not affect a nursing infant.
  • Less likely than regular insulins to cause hypoglycemia.
  • Available in prefilled pens, cartridges, and vials.
  • Less expensive generic versions are available under the name insulin lispro.

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 Humalog. The risk of hypoglycemia increases with tighter blood sugar controls, changes in meal patterns, certain coadministered medications, and changes in physical activity levels. People with liver or kidney disease may be at a higher risk of hypoglycemia. Flu-like symptoms, sore throat, rhinitis, headaches, pain, cough, infection, and nausea are also common side effects.
  • All insulins can cause potassium levels to go low (this is called hypokalemia). Insulin may also cause sodium retention, fluid retention, an increase in weight, mood changes, changes in eyesight and swelling, itching, redness, or lumps around the injection site.
  • The dosage of Humalog needs to be tailored to each individual. Requirements can vary dramatically between people.
  • Humalog must be given with intermediate or long-acting insulin (as a multiple daily injection regimen) or via a continuous subcutaneous infusion device (only Humalog 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.
  • Do not administer the Humalog U-200 intravenously.
  • Use of any insulin, such as Humalog, 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 Humalog works for).
  • If you become pregnant while taking Humalog, 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.

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

Humalog is a fast-acting insulin that may be used in conjunction with either intermediate or long-acting insulin for the treatment of diabetes in adults and type 1 diabetes in children over the age of 3. It acts faster than regular insulin and is less likely to cause hypoglycemia (low blood sugar levels).

5. Tips

  • 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 Humalog for you.
  • The dosage of Humalog 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. There are two different strengths of Humalog: Humalog U-100 and Humalog U-200; however, no dosage conversion is necessary because the dose window shows the number of units to be delivered.
  • Humalog only needs to be given within 15 minutes of a meal. Administer the injection just under the skin of your abdominal wall, thigh, upper arm, or buttocks. Rotate the injection site from one injection to the next. Never share your insulin pen with others.
  • Humalog and other insulin lispro are less likely to cause hypoglycemia than regular insulin
  • Tell your doctor if you have ever had an allergic reaction to any type of insulin before you start using Humalog.
  • Children are especially sensitive to the effects of insulin, particularly around puberty.
  • Never share your Humalog with other people. Store your Humalog as recommended on the label.
  • Inject your Humalog exactly as directed by your doctor. Take all other medications as prescribed.
  • Your insulin requirements may change if you become unwell or develop an infection or other medical conditions. Surgery, injury, mental stress, 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 Humalog in the refrigerator between 36-46 degrees Fahrenheit. Humalog 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 Humalog doesn't heat up; but avoid freezing it. During cold weather, keep your Humalog close to your skin so your body heat keeps it at a more even temperature. Discard any Humalog that you think may have inadvertently got too hot or too cold. The expiry date on Humalog applies to unopened, refrigerated insulin

6. Response and effectiveness

  • Onset 31 minutes; time to peak 50 minutes, duration of action 5.7 to 6.6 hours.
  • Less likely to cause hypoglycemia than regular insulin.
  • Protamine (a fish protein) is added to Humalog to make Humalog lispro protamine suspension. This delays the absorption of lispro insulin and allows it to act for longer in the body. This means people do not have to inject themselves as often. Protamine insulins are cloudy and need to be remixed thoroughly before each injection.

7. Interactions

Medicines that interact with Humalog may either decrease its effect, affect how long it works, increase side effects, or have less of an effect when taken with Humalog. 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 Humalog include:

  • antibiotics, such as doxycycline, minocycline, or sulfonamides
  • 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 beta-blockers (eg, atenolol or bisoprolol) ACE inhibitors (enalapril or captopril), ARBs (eg candesartan or losartan)
  • hormones, such as estradiol, estrone, and norethindrone
  • lithium
  • niacin
  • octreotide
  • orlistat
  • pentamidine
  • pentoxifylline
  • propoxyphene
  • pseudoephedrine
  • salicylates, such as aspirin
  • 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 Humalog 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 Humalog. You should refer to the prescribing information for Humalog 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 Humalog only for the indication prescribed.

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

Copyright 1996-2023 Revision date: July 5, 2023.