Basaglar is a long-acting insulin used to manage blood sugar in people with diabetes. It contains insulin glargine at a concentration of 100 units per milliliter (U-100) and works steadily over the course of a day, making it a once-daily background insulin rather than one you take at meals. It’s FDA-approved for adults and children with type 1 diabetes and for adults with type 2 diabetes.
How Basaglar Works in Your Body
Basaglar is a synthetic version of human insulin, modified so it absorbs slowly from the injection site into your bloodstream. After you inject it, the medication takes about 3 to 4 hours to start lowering blood sugar. Unlike rapid-acting insulins that spike and fade, Basaglar has no real peak. It releases at a relatively flat, steady rate for up to 24 hours, mimicking the low-level background insulin that a healthy pancreas produces between meals and overnight.
This steady profile is why Basaglar is called “basal” insulin. It keeps your blood sugar from drifting too high during the hours when you’re not eating. Most people with type 1 diabetes still need a separate rapid-acting insulin at mealtimes. People with type 2 diabetes may use Basaglar alone or alongside oral medications or mealtime insulin, depending on how well their blood sugar is controlled.
Basaglar is not used to treat diabetic ketoacidosis, a dangerous complication that requires fast-acting insulin and emergency care.
How Basaglar Compares to Lantus
Basaglar is a biosimilar to Lantus, which was the original brand of insulin glargine made by Sanofi. Both contain the same active ingredient at the same concentration. Launched by Eli Lilly and Boehringer Ingelheim, Basaglar was approved in the European Union in 2014 and by the FDA in December 2015, making it the first follow-on biologic insulin in the United States.
Two randomized controlled trials, known as ELEMENT-1 and ELEMENT-2, compared the two products head to head in people with type 1 and type 2 diabetes. Both trials found comparable safety and efficacy. Real-world data from patients who switched from Lantus to Basaglar backs this up: the average change in A1C after switching was just 0.18 percentage points, which was not statistically significant. Daily insulin doses stayed essentially the same as well.
One nuance worth knowing: comparable does not mean officially interchangeable. The FDA has not designated Basaglar as interchangeable with Lantus, which means a pharmacist generally cannot swap one for the other without your prescriber’s approval. In practice, many doctors are comfortable switching patients between the two, often because Basaglar tends to cost less. But the switch should be a deliberate decision, not an automatic substitution at the pharmacy counter.
Common Side Effects
Low blood sugar (hypoglycemia) is the most frequent side effect with any insulin, Basaglar included. In clinical trials, severe hypoglycemia requiring someone else’s help occurred in about 4% of people with type 1 diabetes over 52 weeks and roughly 1% of people with type 2 diabetes over 24 weeks. Mild episodes where you feel shaky, sweaty, or lightheaded but can treat yourself with food or juice are much more common and weren’t tracked the same way.
Other side effects reported at rates of 5% or higher include:
- Injection site reactions: redness, swelling, or itching where the needle goes in
- Weight gain: a common effect of insulin therapy in general
- Swelling (edema): typically mild fluid retention, especially when starting insulin
- Lipodystrophy: lumps or dents in the skin from injecting in the same spot repeatedly
- Allergic reactions: rash, itching, or in rare cases more serious symptoms
Upper respiratory infections and nasopharyngitis (common cold symptoms) also showed up frequently in trial data, though these aren’t necessarily caused by the insulin itself. In the type 1 trial, 16% of participants reported nasopharyngitis over 52 weeks, and 8% reported upper respiratory infections.
How Basaglar Is Taken
Basaglar comes in a prefilled pen called the KwikPen. You inject it under the skin (subcutaneously), typically in the thigh, upper arm, or abdomen, once a day at the same time each day. Rotating your injection site within the same general area helps prevent the skin changes (lipodystrophy) mentioned above.
Your dose is personalized based on your blood sugar readings, your body weight, and what other diabetes medications you’re taking. There’s no standard dose that applies to everyone. If you’re switching from Lantus, most doctors will start you on the same number of units you were already taking, since the two products are clinically comparable.
Basaglar should never be mixed with other insulins in the same syringe or pen, and it should never be injected into a vein or used in an insulin pump.
Storing Your Basaglar Pen
Unopened Basaglar pens belong in the refrigerator, between 36°F and 46°F. Stored this way, they stay effective until the expiration date printed on the package. Once you start using a pen (or if an unopened pen has been left out of the fridge), it can be kept at room temperature, between 59°F and 86°F, for up to 28 days. After 28 days at room temperature, throw it away even if insulin remains inside.
Avoid freezing Basaglar or exposing it to direct heat or sunlight. If the insulin looks cloudy, has particles floating in it, or has changed color, don’t use it. Insulin glargine should be clear and colorless.