If you have diabetes, your doctor may prescribe Humalog.

It’s used to help manage blood sugar levels in adults and some children. And it can be given to people with either type 1 or type 2 diabetes.

Humalog basics

Humalog comes as a solution that you’ll take as an injection. Your doctor may prescribe Humalog as:

  • An injection under your skin. The Humalog KwikPen, Tempo Pen, and Junior KwikPen are three devices that you can use to inject Humalog under your skin.
  • A type of injection under your skin that’s given by an insulin pump. (An insulin pump will inject Humalog under your skin over a period of time.)
  • An intravenous injection, which is an injection into your vein. A doctor or medical provider will give Humalog injections into your vein.

Humalog isn’t a regular insulin. (Regular insulin is short-acting. It works 30 to 60 minutes after it’s given.) Instead, Humalog is classified as a rapid-acting insulin. This type of insulin works 15 minutes after it’s injected. After 1 hour, Humalog reaches its maximum effect in your body. And the drug’s effect in your body lasts between 2 and 4 hours.

Humalog is a biologic medication that contains insulin lispro. A biologic drug is made from parts of living cells. Humalog doesn’t come in a biosimilar form. (Biosimilars are like generic drugs. But unlike generics, which are made for nonbiologic drugs, biosimilars are made for biologic drugs.)

In this article we describe how to take Humalog, its alternatives, side effects, and more.

Your doctor will explain how you should take Humalog. They’ll also explain how much to take and how often. Be sure to follow your doctor’s instructions. Below are commonly used dosages, but always take the dosage your doctor prescribes.

Taking Humalog

Humalog comes as a solution. Your doctor may prescribe Humalog as:

  • An injection under your skin. The Humalog KwikPen, Tempo Pen, and Junior KwikPen are three devices that you can use to inject Humalog under your skin.
  • A type of injection under your skin that’s given by an insulin pump. (An insulin pump will inject Humalog under your skin over a period of time.)
  • An intravenous injection, which is an injection into your vein. A doctor or medical provider will give Humalog injections into your vein.

Humalog contains either 100 units or 200 units of insulin lispro in each milliliter of solution. Your prescription for Humalog may state either “U-100” or “U-200” depending on which strength of the drug your doctor prescribes.

But only Humalog KwikPens come as either U-100 or U-200. Other Humalog pens, vials, and cartridges come only as U-100. (Cartridges hold insulin and are used in reusable insulin pens.)


The best time to administer Humalog is either 15 minutes before you eat or right away after you’ve eaten. Your doctor will tell you how much to take for your doses.

How much Humalog you’ll take varies depending on:

If you’re in a hospital and you need insulin, your doctor may use a dosage scale for Humalog. A dosage scale involves taking small doses of Humalog or another rapid-acting insulin as needed depending on your current blood sugar level. Your healthcare providers will manage your insulin injections if you’re staying in a hospital.

Humalog sliding scale

In the past, doctors would prescribe Humalog on a sliding scale to quickly lower a person’s blood sugar level depending on their blood sugar readings. With a sliding scale, small amounts of Humalog are injected as needed based on your current blood sugar level.

Using a sliding scale requires you to test your blood sugar at home and calculate your insulin dose based on the scale. But this dosage scale is no longer recommended.

According to experts, Humalog sliding scales don’t control blood sugar levels because they’re a reactive treatment. Sliding scales react to your current blood sugar level. But sliding scales don’t manage your insulin needs based on your past blood sugar readings.

Taking Humalog with other drugs

You may need to take other medications together with Humalog to manage your blood sugar levels.

If you’re taking insulin such as Humalog, your doctor may decrease the dosage of, or have you stop taking, other diabetes drugs that increase your insulin level. Doing so helps prevent your blood sugar levels from dropping too low.

Examples of other diabetes medications that may be used with Humalog include:

  • metformin (Glucophage)
  • glyburide (Diabeta)
  • repaglinide (Prandin)
  • acarbose (Glucobay)
  • pioglitazone (Actos)
  • liraglutide (Victoza)
  • sitagliptin (Januvia)
  • saxagliptin (Onglyza)
  • canagliflozin (Invokana)
  • insulin products other than Humalog

If you’d like to know more about taking other drugs with Humalog, talk with your doctor.

Questions about taking Humalog

Below, we answer common questions related to taking Humalog.

  • What if I miss a dose of Humalog? If you miss a dose of Humalog, take the missed dose as soon as you remember. But if it’s been longer than 1 hour since you’ve eaten, just skip the missed dose. Then, take your next dose with your following meal like usual. Your body will start to lower your blood sugar naturally after you eat. So, injecting Humalog more than 1 hour after eating may cause your blood sugar to drop to unsafe levels.
  • Will I need to use Humalog long term? Diabetes, which Humalog is used to manage, is a long-term condition. So you may need to take Humalog long term if your doctor recommends it. Talk with your doctor about how long you’ll need to take this drug.
  • Should I take Humalog with food? You’ll take Humalog either 15 minutes before eating or right away after eating. If you don’t eat, taking Humalog may lower your blood sugar levels to dangerously low levels.
  • How long does Humalog take to work? Humalog works quickly to lower your blood sugar. Within 15 minutes after injection, the drug starts to lower your blood sugar levels. And after 1 hour, Humalog will have its maximum effect in your body. Its effect can last up to 4 hours.
Questions for your doctor

You may have questions about Humalog and your treatment plan. It’s important to discuss all your concerns with your doctor.

Here are a few tips that might help guide your discussion:

  • Before your appointment, write down questions like:
    • How will Humalog affect my body, mood, or lifestyle?
  • Bring someone with you to your appointment if doing so will help you feel more comfortable.
  • If you don’t understand something related to your condition or treatment, ask your doctor to explain it to you.

Remember, your doctor and other healthcare providers are available to help you. And they want you to get the best care possible. So don’t be afraid to ask questions or offer feedback on your treatment.

Humalog and Novolog are both used to manage blood sugar levels in people with diabetes. Novolog contains insulin aspart, while Humalog contains insulin lispro.

Both Humalog and Novolog are rapid-acting insulins, which means they work quickly after they’re injected. But these drugs can’t be substituted for one another.

Novolog can be used in adults and children ages 2 years and older. But Humalog can only be used in adults and children ages 3 years and older.

For a detailed comparison of these two drugs, see our “Humalog vs. Novolog: Important Differences and More” article. And talk with your doctor if you have more questions about these medications.

Find answers to some commonly asked questions about Humalog.

What’s the difference between Humalog and Admelog?

Like Humalog, Admelog is a rapid-acting insulin that’s used to manage blood sugar levels in people with diabetes. (Rapid-acting insulin works 15 minutes after it’s injected.)

Admelog is used in adults and some children with type 1 or type 2 diabetes, just like Humalog is. And Admelog contains the same active ingredient as Humalog: insulin lispro. But Humalog and Admelog can’t be substituted for each other.

Admelog isn’t a biosimilar drug to Humalog. Biosimilars are like generic drugs, which are exact copies of drugs made from chemicals. But unlike generics, which are made for nonbiologic drugs, biosimilars are made for biologic drugs.

Instead, Admelog is a follow-on biologic to Humalog. This means that it was developed by another drug company as their version of Humalog.

Like Humalog, Admelog is taken by injection under your skin or injection into your vein. Additionally, both of these medications can be taken as an injection through an insulin pump. (Insulin pumps continuously deliver insulin into your body.)

If you have more questions about these two drugs, talk with your doctor. They can recommend which medication would be the best treatment option for you.

Are Humalog and Humulin alike?

No, not really. Humalog and Humulin aren’t the same drug. Humulin contains human insulin, while Humalog contains insulin lispro. And different Humulin products also contain different types of insulin.

For example:

  • Humulin-R contains rapid-acting human insulin that’s injected 30 minutes before eating.
  • Humulin-N, on the other hand, contains a type of human insulin called isophane insulin. It’s an intermediate-acting insulin that takes longer to start working and lasts longer in your body.
  • And another product called Humulin 70/30 contains a mixture of rapid and intermediate-acting human insulin.

If you’d like to know more about the differences and similarities of Humalog and Humulin, see this drug article. And be sure to talk with your doctor about which drug is right for you.

How fast does Humalog work?

The onset of Humalog’s action is 15 minutes after it’s injected. This means that the action time starts 15 minutes after you take a Humalog injection. And the drug’s action time lasts about 2 to 4 hours, with a peak effect after 1 hour. (Peak effect is when the drug has its maximum effect in your body.)

Humalog is a rapid-acting insulin, but it loses its effect quickly. This is unlike long-acting insulin, which takes longer to start working, but is longer lasting.

How long does Humalog last in your body?

Humalog can last about 4 to 5 hours in your body.

The drug’s half-life is 1 hour. This means that half of a dose of Humalog will be eliminated by your body after 1 hour. In general, after about four to five half-lives, a medication reaches very low levels and is eliminated from your body.

Does Humalog need to be refrigerated?

Yes, unopened Humalog needs to be refrigerated until you’re ready to use it. After getting Humalog from your pharmacy, you should place the unopened drug into your refrigerator. And make sure the temperature is between 36°F and 46°F (2°C and 8°C).

Once you open Humalog, you can store vials, cartridges, and prefilled pens at room temperature, but below 86°F (30°C). But you’ll have to use the product within 28 days. Any unused insulin should be discarded after 28 days if kept at room temperature.

Like most drugs, Humalog may cause mild or serious side effects. The lists below describe some of the more common side effects that Humalog may cause. These lists don’t include all possible side effects.

Keep in mind that side effects of a drug can depend on:

  • your age
  • other health conditions you have
  • other medications you may be taking

Your doctor or pharmacist can tell you more about the potential side effects of Humalog. They can also suggest ways to help reduce side effects.

Mild side effects

Here’s a short list of some of the mild side effects that Humalog can cause. To learn about other mild side effects, talk with your doctor or pharmacist, or read the patient information for Humalog U-100 and Humalog U-200.*

Mild side effects of Humalog that have been reported, and are discussed below in “Side effect focus” include:

Mild side effects of many drugs may go away within a few days or a couple of weeks. But if they become bothersome, talk with your doctor or pharmacist.

* Humalog U-100 and U-200 are different strengths of Humalog. For more information, see the “How is Humalog taken?” section above.

Serious side effects

Serious side effects from Humalog can occur, but they aren’t common. If you have serious side effects from Humalog, call your doctor right away. But if you think you’re having a medical emergency, you should call 911 or your local emergency number.

Serious side effects of Humalog that have been reported include:

* For more information on this side effect, see the “Side effect focus” section below.

Side effect focus

Learn more about some of the side effects Humalog may cause.

Weight gain

You can gain weight while you’re taking Humalog, or any other insulin product.

Experts say that this happens because with treatment of high blood sugar levels, you’re no longer urinating as often or as much as before. And insulins are used to manage high blood sugar levels.

Also, insulin helps your body’s cells absorb sugar from your bloodstream. But when your cells absorb too much sugar, your body makes fat. And this may lead to weight gain.

What might help

Your dose of insulin may need to be adjusted if you gain or lose weight during treatment. Talk with your doctor if you’re concerned about your weight and your dosage of Humalog.

If you’re gaining weight with Humalog, ask your doctor about ways to manage your nutrition and level of physical activity. Your doctor can help you develop a plan to manage your weight. Additionally, a nutritionist may be able to help you plan meals that are beneficial for people with diabetes. And an exercise specialist can suggest ways to add physical activity into your lifestyle.

Low blood sugar level

If you have a low blood sugar level, which is also called hypoglycemia, you shouldn’t take Humalog. This is because the drug will lower your blood sugar even more.

Usually, hypoglycemia occurs when your blood sugar level is below 70 milligrams/deciliter (mg/dL). The normal range for fasting blood sugar level in people with diabetes is 80 mg/dL to 130 mg/dL.

Symptoms of low blood sugar can include:

  • anxiety or nervousness
  • sweating or having chills
  • irritability, impatience, or confusion
  • fast heart rate
  • dizziness
  • skin that looks paler than usual
  • blurred or impaired vision
  • headache

What might help

When injecting insulin, including Humalog, you should be aware of the symptoms of low blood sugar levels. And be sure to check your blood sugar levels per your doctor’s instructions.

Additionally, to help prevent low blood sugar, follow your doctor’s instructions for taking Humalog.

If you do have low blood sugar with Humalog, make sure to consume something with sugar that can be quickly absorbed by your body. Such items include:

  • sugar tablets or gel
  • 4 ounces of juice or regular soda (not sugar-free or diet versions)
  • 1 tablespoon of sugar, honey, or corn syrup
  • hard candies, jellybeans, or gumdrops

To raise your blood sugar level, you’ll need to ingest 15 grams (g) of sugar. If your blood sugar still hasn’t increased after 15 minutes, you should ingest another 15 g of sugar.


It’s possible to have lipodystrophy while you’re using Humalog. This condition causes changes in the way fat tissue is distributed in your body. It can occur when you inject insulin, such as Humalog, into the same area.

With lipodystrophy, you may have pitting or thickened areas on your skin.

What might help

You’ll inject Humalog under the skin of your stomach, thigh, arm, or buttocks. To help prevent lipodystrophy, you’ll need to change your injection site each time you inject the drug. This means you’ll avoid injecting into the exact same spot for each injection.

You should also avoid injecting into areas of your body that already have altered fat distribution. These areas may look pitted, thickened, or lumpy. Also, don’t inject Humalog where your skin is tender, scarred, or damaged.

Allergic reaction

Some people may have an allergic reaction to Humalog.

Symptoms of a mild allergic reaction can include:

  • skin rash
  • itchiness
  • flushing (warmth, swelling, or redness, or discoloration in your skin)

A more severe allergic reaction is rare but possible. Symptoms of a severe allergic reaction can include swelling under your skin, typically in your eyelids, lips, hands, or feet. They can also include swelling of your tongue, mouth, or throat, which can cause trouble breathing.

Call your doctor right away if you have an allergic reaction to Humalog. But if you think you’re having a medical emergency, call 911 or your local emergency number.

Some important things to discuss with your doctor when considering Humalog include:

  • your overall health
  • any medical conditions you may have

Also, tell your doctor if you’re taking any medications. This is important to do because some drugs can interfere with Humalog.

These and other considerations are described below.


Taking medications, vaccines, foods, and other things with a certain drug can affect how the drug works. These effects are called interactions.

Before taking Humalog, be sure to tell your doctor about all medications you take (including prescription and over-the-counter types). Also describe any vitamins, herbs, or supplements you use. Your doctor or pharmacist can tell you about any interactions these items may cause with Humalog.

Interactions with drugs or supplements

Humalog can interact with several types of drugs. These drugs include:

This list does not contain all types of drugs that may interact with Humalog. Your doctor or pharmacist can tell you more about these interactions and any others that may occur with use of Humalog.


Humalog may not be suitable for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before you take Humalog. Factors to consider include those in the list below.

  • Hypoglycemia. Low blood sugar (hypoglycemia) can be life threatening. Your doctor may suggest increasing how often you check your blood sugar levels when you first start Humalog or whenever your dosage is changed. During these times, you have a higher risk for hypoglycemia with Humalog.
  • Allergic reaction. If you’ve had an allergic reaction to Humalog or any of its ingredients, you shouldn’t take Humalog. Ask your doctor what other medications are better options for you.
  • Low blood potassium levels. If you have low potassium levels in your blood, taking Humalog may be dangerous. If you develop low potassium levels during treatment with Humalog, your doctor may tell you to stop taking the drug. Your doctor may also have you take supplements to raise your potassium levels.

Use with alcohol

Alcohol can affect Humalog’s effect in lowering your blood sugar level.

Specifically, alcohol can cause insulin, such as Humalog, to act stronger than usual. And this can increase your risk for low blood sugar and other side effects.

Be sure to tell your doctor if you drink alcohol. Let them know how much and how often you drink. Your doctor may adjust your Humalog dosage if needed. Don’t drink alcohol or take medications that contain alcohol while using Humalog before first talking with your doctor.

Pregnancy and breastfeeding

Doctors don’t have enough information on whether Humalog is harmful if used by pregnant people.

Studies show that Humalog doesn’t increase the risk of major developmental issues, miscarriage, or other problems during pregnancy. And there’s more risk for a pregnant person and their fetus if diabetes isn’t well-managed during pregnancy.

Currently, doctors aren’t sure whether Humalog:

  • passes into human breast milk, or
  • has an effect on a child who is breastfed or your body’s milk production

If you’re pregnant or breastfeeding, talk with your doctor about the benefits and risks of taking Humalog.

Costs of prescription drugs can vary depending on many factors. These factors include what your insurance plan covers and which pharmacy you use. To find current prices for Humalog in your area, visit GoodRx.com.

If you have questions about how to pay for your prescription, talk with your doctor or pharmacist. You can also visit the Humalog manufacturer’s website to see if it has support options.

If you have diabetes, your doctor may prescribe Humalog.

It’s used in adults and children ages 3 years and older. The drug works to help manage blood sugar levels. And it can be given to people with either type 1 or type 2 diabetes.

With diabetes, your body either doesn’t make enough insulin, or it doesn’t respond to insulin normally. Insulin is a hormone that helps lower your blood sugar level. It brings sugar out of your blood and into your cells, where the sugar is used for energy. So, with diabetes, your blood sugar level is higher than normal.

Humalog contains a type of insulin called insulin lispro. It lowers your blood sugar levels by:

  • helping your muscle and fat cells take in sugar from your blood
  • blocking your liver from making sugar
  • stopping your body’s breakdown of fat and protein so that your body will use up sugar instead

Don’t take more Humalog than your doctor prescribes. Using more than this can lead to serious side effects.

If you take too much Humalog, your blood sugar may drop too low, causing hypoglycemia (low blood sugar level). A severe overdose of Humalog can cause your blood sugar to drop very low, which can be life threatening.

Symptoms of severe hypoglycemia

Overdose of Humalog can cause severe hypoglycemia, which may lead to these symptoms:

What to do in case you take too much Humalog

If you have a glucagon injection available, ask someone to inject you with it if you’re unable to do so yourself. (Glucagon will quickly raise your blood sugar level.)

Also, call your doctor if you think you’ve taken too much Humalog. You can also call 800-222-1222 to reach the American Association of Poison Control Centers, or use its online resource. But if you have severe symptoms, immediately call 911 (or your local emergency number) or go to the nearest emergency room.

Note: If you haven’t already, be sure to talk with your doctor about when and how to use glucagon.

If you have questions about taking Humalog, talk with your doctor or pharmacist. Your doctor can tell you about other treatments you can use for your condition. Here’s a list of articles that you might find helpful.

Some questions to ask your doctor about Humalog may include:

  • How can I store Humalog if I am traveling to a warmer climate?
  • How often do I need to check my blood sugar level while I’m taking Humalog?
  • What should I do if I notice pits, thickened areas, or lumps of fat develop around my stomach?
  • How often do I need to change out Humalog needles?

You can learn more about the uses of Humalog by subscribing to Healthline’s type 2 diabetes newsletter.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up-to-date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or other healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.