Lantus vs. Semglee: 7 Ways These Long-Acting Insulins Compare

If you’re living with diabetes and insulin is part of your treatment plan, there are several long-acting insulin options to choose from. Lantus (insulin glargine) has been around the longest. But there’s also a Lantus alternative called Semglee (insulin glargine-yfgn) on the market.

While Lantus and Semglee aren’t exactly the same, you can substitute one for the other. So, how do Lantus and Semglee compare? We discuss seven things you should know below.

1. Semglee is interchangeable with Lantus

Lantus is a long-acting insulin that has been around for over 20 years. It’s also a biologic medication. That means it’s made using a living system and regulated differently from chemical-based medications, such as blood pressure pills.

Lantus is a brand-name insulin. Manufacturers can’t make copies — or generic versions — of biologics. Instead, they can make biosimilars. Biosimilars are biologics that are highly similar to another FDA-approved biologic.

Semglee is a long-acting insulin that was first approved in June 2020. In July 2021, it became the first interchangeable biosimilar to Lantus. This means it’s highly similar to Lantus, and it has gone through additional studies to show that you can switch between products without issues.

Since it’s interchangeable, your pharmacist can more easily substitute Semglee for Lantus without contacting your prescriber first. This is similar to how your pharmacist may switch you from a brand-name medication to a generic.

Semglee and another insulin called Rezvoglar (insulin glargine-aglr) are both interchangeable biosimilars to Lantus. Basaglar (insulin glargine) is considered a follow-on biologic version of Lantus. That’s because it was approved before insulin needed to go through the biosimilar approval pathway. Basaglar isn’t considered to be interchangeable with Lantus.

2. Lantus and Semglee work the same way for diabetes

Lantus and Semglee are both types of insulin. Insulin is an important hormone in your body. It helps regulate your blood glucose (blood sugar) levels and prevents them from getting too high. Some people with diabetes may need to supplement insulin if they don’t make enough or if their body is resistant to the insulin they make.

Long-acting insulins, such as Lantus and Semglee, are slowly released and absorbed by the body, providing a steady amount of insulin for up to 24 hours. They work in the background to manage your blood sugar levels, even when you’re not eating.

Lantus or Semglee may be used in combination with faster-acting insulins throughout the day to help keep your blood sugar levels within your target range.

3. Lantus and Semglee are available in the same dosage forms and are given the same way

Both Lantus and Semglee are administered as subcutaneous (under-the-skin) injections once daily. It doesn’t matter what time of day, but it should be at the same time every day.

Injection sites include the thigh, stomach area, and upper arm. It’s recommended to rotate where you inject each time to avoid hard lumps or fatty deposits from forming. Always use a new needle with each injection — don’t reuse needles.

How much insulin you should inject is individualized to your specific needs. Follow your prescriber’s instructions to ensure you’re giving yourself the correct dose.

Lantus and Semglee are available in vials and prefilled injection pens. Injection pens can be a good option if you have difficulty drawing your insulin dose from a vial.

4. Lantus and Semglee are similarly effective for diabetes

Semglee contains a slightly different form of insulin glargine called insulin glargine-yfgn. But since it’s a biosimilar to Lantus, there are no clinically meaningful differences between the two products. This means that Semglee is just as effective as Lantus in managing blood sugar levels. You should expect similar results if you switch from Lantus to Semglee (or vice versa).

Since Lantus and Semglee provide similar benefits, factors such as insurance coverage and cost may ultimately determine which option is right for you. More on that later.

5. Lantus and Semglee can cause similar side effects

As with all insulins, Lantus and Semglee can cause side effects, which should be similar between products. Examples of these include:

• Low blood sugar (hypoglycemia)

• Hard lumps or fatty deposits (lipodystrophy)

• Injection site reactions, such as swelling, redness, and pain

• Itchy skin

• Swelling in hands or feet

• Weight gain

• Rash

• Low potassium levels (hypokalemia)

Some side effects can be avoided or minimized by rotating injection sites and carefully monitoring your blood sugar levels.

6. Lantus and Semglee have similar interactions

Lantus and Semglee can both interact with other medications that lower blood sugar levels. These combinations can increase the risk of hypoglycemia. Examples include:

• Sulfonylureas, such as glipizide (Glucotrol XL)

• Meglitinides (glinides), such as repaglinide

• Glucagon-like peptide-1 receptor agonists, such as semaglutide (Ozempic, Wegovy, Rybelsus)

• Fluoroquinolone antibiotics, such as ciprofloxacin

• Sulfa antibiotics, such as sulfamethoxazole / trimethoprim (Bactrim)

There are also some medications and supplements that can increase blood sugar levels, making Lantus and Semglee less effective. Examples include corticosteroids and antipsychotic medications.

Make sure your prescriber and pharmacist know all of the medications you’re taking. This includes over-the-counter products and supplements. This can help you avoid or manage potential interactions.

7. Lantus and Semglee are both available as unbranded insulins

Lantus is available as a brand-name insulin product, while brand-name Semglee has been discontinued. However, both insulins are available as unbranded products. This is similar to the concept of authorized generics.

The unbranded biologic for Lantus is called insulin glargine U-100. It’s the same product as Lantus, but without the brand name. This is also the case for unbranded Semglee, called insulin glargine-yfgn.

How to save on Lantus and Semglee

There are ways to save on Lantus and unbranded Semglee. GoodRx can help you navigate the ways to save on your insulin prescription.

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Written 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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