Ross is a writer for Verywell with years of experience practicing pharmacy in various settings. She is also a board-certified clinical pharmacist and the founder of Off Script Consults.

Erika Prouty, PharmD, is a professional community pharmacist who aids patients in medication management and pharmacy services in North Adams, Massachusetts.

Humalog (insulin lispro injection) is a prescription rapid-acting injectable insulin analog (eg., it's a manufactured insulin). This medication is used to treat diabetes. It works by lowering blood glucose (sugar) in the body.

Administration Route(s): Subcutaneous, intravenous

Humalog is a treatment option for type 1 and also type 2 diabetes (high blood sugar). In the United States, the Centers for Disease Control and Prevention (CDC) estimates that diabetes affects more than 37 million people—with prediabetes (when blood sugar is high but not high enough to be diagnosed as diabetes) affecting an additional 96 million people.

The National Diabetes Prevention Program (DPP) helps prevent or delay diabetes in people with prediabetes. If you have prediabetes and would like to know more about chapters of the DPP in your area, ask your healthcare provider for more information or contact a local program.

If you have diabetes, you might experience the following symptoms:

Over time, uncontrolled high blood sugar levels can lead to diabetes-related complications, including neuropathy (nerve pain or numbness), diabetic foot sores, amputations, eye problems, and kidney impairment.

Diabetes can also raise your risk of heart disease and stroke, which are the leading causes of death in the United States.

In general, when using Humalog, take the following precautions:

Your healthcare provider can recommend which route you’ll use for your Humalog, which includes:

If you’re going to inject Humalog under your skin (subcutaneous), the specific directions will vary per person. Use Humalog according to your healthcare provider’s recommendations. The following, however, are some typical steps to inject Humalog under your skin.

After bringing Humalog home from the pharmacy, you’ll need to protect your insulin from heat and light. Also, avoid freezing insulin. You can place unused vials and pens in your refrigerator between 36 degrees and 46 degrees. These refrigerated and unused vials and pens will last until the expiration date on the container or packaging.

If you prefer to store your unopened vials or unused pens at room temperature, however, then these products will only last for 28 days. Once you open a Humalog vial, you can store it in your fridge or at room temperature. But you will need to throw it away after 28 days. Once you use a Humalog pen, on the other hand, you can only store it at room temperature. And after 28 days, you will also need to throw it away.

If your healthcare provider recommends diluted (watered down) Humalog U-100 for you to inject under your skin, your healthcare provider will help you dilute your insulin in an appropriate amount and type of liquid. This diluted Humalog U-100 will be in good condition for 28 days in your refrigerator at 41 degrees. If you’re going to store your diluted Humalog U-100 at 86 degrees—which is above room temperature, your insulin will expire in 14 days.

If you are going to travel with Humalog, familiarize yourself with the regulations of your final destination. Make a copy of your Humalog prescription and consider asking your healthcare provider for documentation of medical necessity on a letter with an official letterhead. Also, have the original packaging or container with your name on it—from your pharmacy.

If you are carrying empty syringes, make sure to have Humalog physically on your person. You may also want to have an insulated bag with cold packs to prevent your insulin from getting too hot.

Humalog lowers your blood sugar very quickly. The manufacturer recommends injecting this insulin within 15 minutes before or immediately after a meal.

Similar to other insulins, side effects are possible with Humalog.

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the Food and Drug Administration (FDA) at fda.gov/medwatch or 800-FDA-1088.

Common side effects with Humalog include:

Seek immediate medical attention if you experience any of the following severe side effects:

Repeatedly using the exact same injection or insertion (infusion) spot raises your risk of lipodystrophy, which is an abnormal distribution of fat. This medical condition can lead to pitted-looking skin due to thinning of your fat tissue. It can also cause thick-looking skin due to the thickening of fat tissue.

Humalog may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

Pregnant people: In reference to currently available data, there is no connection between using Humalog and negative effects on your unborn fetus. Uncontrolled diabetes, however, can raise your chance of miscarriage, preterm birth, stillbirth and delivery complications. Be sure to discuss any concerns with your healthcare provider.

Breastfeeding people: Data about the effect of Humalog on nursing babies are lacking. Discuss any questions that you may have about using Humalog while nursing with your healthcare provider.

Children: The FDA approved Humalog to treat type 1 diabetes in children. You can use Humalog as under-the-skin injections. You can also use Humalog U-100 in an infusion pump. The manufacturer of this medicine, however, hasn’t studied Humalog for use in children under 3 years old or in children with type 2 diabetes.

People with kidney or liver problems: People with kidney or liver problems have a higher risk of low blood sugar with Humalog. As a result, your healthcare provider may recommend closely monitoring your blood sugar and adjusting your insulin dose as needed.

Humalog is typically used 15 minutes before or right after a meal. If you remember your missed Humalog dose before or right after mealtime, then immediately inject your missed dose. If some time (e.g., more than one hour) has passed since your missed dose, you can usually wait until your next scheduled meal and dosing time.

If you’re using Humalog in your insulin pump, perform the following maintenance tasks as soon as you remember:

Don’t try to double up and use extra insulin to make up for missed doses.

Since next steps to take after a missed Humalog dose will vary per person, refer to your healthcare provider’s recommendations. If you still have questions or concerns, call your healthcare provider.

Do your best to work toward finding ways to regularly remember your Humalog doses and insulin pump maintenance tasks. Forgetting doses and insulin pump maintenance tasks can cause uncontrolled high blood sugar levels and side effects. Over time, these high blood sugar levels can result in diabetes-related complications—like amputations, eye problems, heart disease, kidney problems and stroke.

If you accidentally use too much Humalog, you may experience low blood sugar symptoms—like fast heartbeat, hunger, irritability, sweating, and tremors. So, if your blood sugar isn’t too low, use the following “15-15 rule”:

If you’re experiencing clumsiness, coma, confusion and seizures, then your blood sugar is too low for the 15-15 rule. You may need to use the glucagon product that your healthcare provider prescribed. Glucagon is a naturally occurring hormone that encourages your liver to release glucose (sugar) into the bloodstream.

Since extremely low blood sugar is also linked to low potassium, get medical help right away—even after using your glucagon prescription. You might need hospital observation until your blood sugar and potassium levels reach normal ranges again.

If you think you or someone else may have overdosed on Humalog, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Humalog, call 911 immediately.

Never share insulin pens or cartridges with others under any circumstances. It is not safe for one pen to be used for more than one person. Sharing needles or pens can result in transmission of hepatitis viruses, HIV, or other bloodborne illnesses.

Your doctor will want to check your progress at regular visits, especially during the first few weeks you take this medicine. Blood tests may be needed to check for unwanted effects.

It is very important to follow carefully any instructions from your health care team about:

In case of emergency: There may be a time when you need emergency help for a problem caused by your diabetes. You need to be prepared for these emergencies. It is a good idea to:

This medicine may cause a serious allergic reaction, including anaphylaxis, which can be life-threatening and requires immediate medical attention. Tell your doctor right away if you have a rash, itching, shortness of breath, swelling of the face, tongue, and throat, trouble breathing, or chest pain after you receive this medicine.

You may have some skin redness, rash, itching, or swelling at the injection site. If this irritation is severe or does not go away, call your doctor. Do not inject insulin lispro into a skin area that is red, swollen, or itchy.

Using this medicine together with other diabetes medicine (eg, pioglitazone, rosiglitazone, Actos®, Actoplus Met®, Avandia®) may cause serious heart problems or edema (fluid retention). Check with your doctor immediately if you are rapidly gaining weight, having shortness of breath, chest pain or discomfort, extreme tiredness or weakness, trouble breathing, uneven heartbeat, or excessive swelling of the hands, wrist, ankles, or feet.

Too much insulin lispro can cause hypoglycemia (low blood sugar). Low blood sugar can also occur if you use insulin lispro with another antidiabetic medicine, changes in insulin regimen (eg, insulin strength, type of insulin, injection site), delay or miss a meal or snack, exercise more than usual, drink alcohol, or cannot eat because of nausea or vomiting or have diarrhea. Low blood sugar must be treated before it causes you to pass out (unconsciousness). People feel different symptoms of low blood sugar. It is important that you learn which symptoms you usually have so that you can treat it quickly. Talk to your doctor about the best way to treat low blood sugar.

Symptoms of low blood sugar include anxiety, behavior change similar to being drunk, blurred vision, cold sweats, confusion, depression, difficulty in thinking, dizziness or lightheadedness, drowsiness, excessive hunger, fast heartbeat, headache, irritability or abnormal behavior, nervousness, nightmares, restless sleep, shakiness, slurred speech, and tingling in the hands, feet, lips, or tongue.

If symptoms of low blood sugar occur, eat glucose tablets or gel, corn syrup, honey, or sugar cubes, or drink fruit juice, non-diet soft drink, or sugar dissolved in water to relieve the symptoms. Also, check your blood for low blood sugar. Go to a doctor or a hospital right away if the symptoms do not improve. Someone should call for emergency help immediately if severe symptoms, such as convulsions (seizures) or unconsciousness occur. Have a glucagon kit available, along with a syringe and needle, and know how to use it. Members of your household should also know how to use it.

Hyperglycemia (high blood sugar) may occur if you do not take enough or skip a dose of your antidiabetic medicine or insulin, changes in insulin regimen, you overeat or do not follow your meal plan, have a fever or infection, or do not exercise as much as usual. High blood sugar can be very serious and must be treated right away. It is important that you learn which symptoms you have in order to treat it quickly. Talk to your doctor about the best way to treat high blood sugar.

Symptoms of high blood sugar include blurred vision, drowsiness, dry mouth, flushed, dry skin, fruit-like breath odor, increased urination, ketones in the urine, loss of appetite, stomachache, nausea or vomiting, tiredness, troubled breathing (rapid and deep), unconsciousness, and unusual thirst. If these symptoms occur, check your blood sugar level and then call your doctor for instructions.

This medicine may make you dizzy or drowsy. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.

The manufacturer recommends against using Humalog if the following applies to you:

Use caution with the following medications:

This isn’t a complete list of medications that can interact with Humalog. For more detailed information about medications that interact with Humalog, talk with your pharmacist or healthcare provider.

There are many different types of insulin. Humalog is a rapid-acting insulin, which is usually given around mealtime.

All of the above insulins are rapid acting except for the human regular insulin products, which are short acting. Compared to rapid-acting insulins that are given within 15 minutes of meals, short-acting insulins are given within 30 minutes of meals. While these two types of insulins are slightly different, these insulins have no differences in achieving blood sugar goals and lessening low blood sugar symptoms.

Additionally, unlike the rapid-acting insulins, some of the short-acting ones—like Humulin R and Novolin R—are available as over-the-counter (OTC) medications, which don’t require a prescription from your healthcare provider. As OTC products, the short-acting insulins might also be less costly than the rapid-acting insulins—even without insurance coverage.

Since all of these insulins are mealtime insulins, they’re not typically used together for diabetes. If you have any questions or concerns, talk with your pharmacist or healthcare provider.

Humalog is available as a prescription from your healthcare provider. Many of your local retail pharmacies will carry Humalog in the refrigerator behind the pharmacy counter. If necessary, the pharmacy staff can also order this insulin for you.

Humalog is a brand-name insulin product. So, it might be costly without insurance coverage. If cost is a concern, consider talking with your pharmacist or healthcare provider about switching to the generic version or changing to one of the OTC short-acting insulins. You can also reach out to the manufacturer for more information about discounts.

In addition to Humalog, many people also have a basal insulin to help them achieve their fasting blood sugar goals.

Basal insulin is another type of insulin that mimics the background (baseline) insulin in people without diabetes who typically release a certain amount of insulin 24 hours throughout the day regardless of what food or beverages they’ve had. 

Fasting blood sugar is your blood sugar without any food for at least eight hours. Many people measure this blood sugar level in the morning after a full night of sleep without food.

You can only give yourself up to 60 units with one injection from many of the KwikPens. For the Junior KwikPen, however, this pen will only allow up to 30 units for one injection. If your healthcare provider recommended a dose higher than 60 units for most KwikPens or 30 units for the Junior KwikPen, then you will need to give yourself more than one injection.

Also, you cannot select a dose that is more than the number of units left in the KwikPen. So, if you need more units than what is left in your KwikPen, you can inject the amount that is left in this pen. Then, use a new pen to inject the rest of your dose. Another option is to throw away the used KwikPen—without a needle—in your regular trash and use a brand new pen to inject the full insulin dose.

Remember to use a new needle for each injection.

In addition to regularly taking or using your medications for diabetes, there are other ways to stay healthy, which include the following:

Maintaining a healthy lifestyle can help you have well-controlled blood sugar and prevent diabetes-related complications.

Verywell Health's drug information is meant for educational purposes only and is not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

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Food and Drug Administration. Humalog label.

Centers for Disease Control. Diabetes Basics.

Centers for Disease Control. Diabetes Symptoms.

Centers for Disease Control. Diabetes: Coexisting Conditions and Complications.

Centers for Disease Control. Stroke.

Centers for Disease Control. Heart Disease.

National Institutes of Health. What is Diabetes?

American Diabetes Association. Hyperglycemia (high blood sugar).

American Heart Association. Warning Signs of Heart Failure.

American Diabetes Association. Hypoglycemia (low blood sugar).

American Diabetes Association. Introduction: Standards of Medical Care in Diabetes—2022. Diabetes Care. 2022 Jan;45(Supplement_1):S1-2.

Food and Drug Administration. Novolin R label.

Food and Drug Administration. Humulin R label.

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