7 NovoLog Side Effects and How to Manage Them

If you’re living with diabetes, your healthcare provider may prescribe NovoLog (insulin aspart) — a rapid-acting insulin that you inject before you eat. NovoLog starts working quickly and lasts for up to 5 hours to help control post-meal blood glucose (sugar) spikes.

Like any insulin, NovoLog can cause side effects. Low blood glucose (called hypoglycemia) is most common. But weight gain, injection site reactions, and headaches are possible, too.

Fortunately, many NovoLog side effects can be managed by monitoring your blood glucose and fine-tuning your injection technique. Below are seven NovoLog side effects you may encounter, plus tips for how to manage them.

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1. Hypoglycemia

Hypoglycemia is a common NovoLog side effect. After injecting your dose, it’s possible for your blood glucose to drop too low — below 70 mg/dL.

The risk of hypoglycemia can go up if you take NovoLog with other diabetes medications. Skipping meals, drinking alcohol, and fighting off an infection are a few other factors that can also increase this risk.

If your blood glucose is low, common symptoms can include:

• Fast heartbeat

• Feeling shaky

• Confusion

• Dizziness

• Sweating

• Hunger

If you start to feel any of these symptoms, check your blood glucose. If it’s below 70 mg/dL, use the 15-15 rule to raise it back up. This involves taking 15 g of fast-acting carbohydrates (e.g., 4 glucose tablets), waiting 15 minutes, and then checking your blood glucose again. Repeat this process until your blood glucose is greater than 70 mg/dL. Blood glucose below 55 mg/dL is considered severe and may need medical attention.

If you’re frequently experiencing hypoglycemia episodes with NovoLog, inform your healthcare provider. This can be a sign that your insulin dose is too high and needs to be adjusted.

2. Injection site reactions

NovoLog, like most types of insulin, is given as an injection. This can sometimes lead to reactions at or around the area where you inject your dose. Common injection site reactions may include:

• Redness

• Swelling

• Itching

• Warmth

• Mild pain or discomfort

Injection site reactions from NovoLog typically go away on their own after a few days. In the meantime, a warm compress, ice packs, or over-the-counter (OTC) pain relievers may give some relief.

Pharmacist tip: Using proper injection technique can help prevent injection site reactions from happening, or lessen their severity. It’s also important to rotate where you inject each time and avoid injecting into irritated skin.

3. Lipodystrophy

Lipodystrophy is the most common skin-related NovoLog side effect. This is where there’s a problem with the fatty tissue underneath your skin — resulting in thickened or pitted areas. Lipodystrophy can develop where you inject NovoLog.

Similar to injection site reactions, rotating where you inject NovoLog each time can help prevent lipodystrophy. But if you find thickened areas, pits, or lumps in your skin, avoid injecting into those spots since this can affect how you absorb your NovoLog dose.

4. Swelling

While uncommon, NovoLog can cause swelling in your hands and feet. This is because insulin can cause your body to hang onto sodium and fluid.

Swelling isn’t always a cause for concern. But it can be an issue if you have heart failure or kidney problems. Swelling may be more likely if you’re taking NovoLog with a thiazolidinedione medication, like pioglitazone (Actos). This combination can potentially worsen heart failure symptoms.

In many cases, swelling should improve over time. But in the meantime, your healthcare provider may suggest elevating your legs and reducing your salt intake to help lessen any swelling. If that doesn’t help, or if your swelling gets worse, they can determine the best next steps.

5. Weight gain

Insulin is a very effective medication for blood glucose control due to how it works in your body. But, these effects can also lead to weight gain. The average weight gain seen with insulin therapy is about 4 lbs during the first year. Keep in mind that fluid retention can also cause weight changes.

If weight gain is a concern for you, talk to your healthcare provider about ways to manage it. This may include adjustments to your diabetes-friendly diet, as well as regular exercise. And if weight management is part of your treatment goals, they may add a diabetes medication that can cause weight loss, such as Ozempic (semaglutide).

6. Headache

You may experience headaches after starting NovoLog or adjusting your dose. This can happen as your body gets used to the blood glucose changes and should improve over time. But headaches can also be a sign that your blood glucose is too high or too low.

If you feel a headache coming on and you’re unsure of the cause, checking your blood glucose level is a good place to start. If it’s too high or too low, follow instructions given by your provider to bring your blood glucose to a safe level. But if it’s within a normal range for you, your healthcare provider may suggest an OTC pain reliever for relief in the meantime.

If your headaches don’t seem to be going away, or if they’re getting worse, talk to your healthcare provider since headaches can have many causes beyond insulin. They can figure out the best next steps.

7. Diarrhea

Diarrhea is a commonly reported side effect for people who take NovoLog for Type 1 diabetes. Similar to headaches, diarrhea can happen when you start a new medication and will typically get better on its own.

If you’re experiencing diarrhea, make sure to drink plenty of fluids and try sticking to bland foods for a period of time since they’re easier to digest. Your pharmacist or provider may also suggest an ​​OTC diarrhea medication, like loperamide (Imodium A-D) and bismuth subsalicylate (Pepto-Bismol).

When should you contact your healthcare provider about NovoLog side effects?

Many NovoLog side effects are mild and should go away on their own. Others can be managed by adjusting your injection technique, rotating where you inject, and making certain lifestyle changes.

But, there are some NovoLog side effects, like hypoglycemia, that can be life-threatening if left untreated. Contact your healthcare provider if you’re having hypoglycemia episodes, as they may want to adjust your NovoLog dose.

It’s understandable that even mild medication side effects can be difficult to tolerate, and sometimes people stop taking their medications because of them. But, you shouldn’t stop NovoLog without talking to your provider first. If needed, they can discuss your options and any potential changes to your treatment plan with you.

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Written by:

Hope Chang, PharmD, AAHIVP

Hope Chang is a freelance writer and content reviewer for GoodRx. She attended Howard University College of Pharmacy in Washington, D.C. and completed post-graduate residency training at the University of California, Davis Medical Center.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

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