Basaglar is insulin glargine. It has the exact same amino acid sequence as Lantus, the original brand of insulin glargine, and works the same way in your body. The difference is that Basaglar is made by a different manufacturer using a different production process, which is why it exists as a separate product with a separate name and a lower price point.
If you’ve been prescribed one and are wondering whether you can use the other, or if your pharmacy switched you and you want to know what changed, here’s what actually matters.
Same Molecule, Different Manufacturer
Lantus, the original insulin glargine, is made by Sanofi. Basaglar is made by Eli Lilly and Boehringer Ingelheim. Both use genetically modified E. coli bacteria to produce the insulin, but their manufacturing processes differ. Think of it like two factories producing the same chemical compound: the end product is identical in structure, but the equipment, purification steps, and quality checks vary between facilities.
Because insulin glargine is a large, complex biological molecule rather than a simple chemical like ibuprofen, regulators treat copies differently than they treat generic pills. Lilly couldn’t just prove the chemical formula matched. They had to run clinical trials comparing Basaglar directly against Lantus to show the two performed equivalently in real patients.
How Basaglar Performed Against Lantus in Trials
The FDA reviewed head-to-head trials in both type 1 and type 2 diabetes before approving Basaglar. In people with type 1 diabetes, Basaglar lowered HbA1c by 0.35 percentage points over the study period, compared to 0.46 points for Lantus. That difference of 0.11 percentage points was not statistically significant. In type 2 diabetes, the gap was even smaller: Basaglar reduced HbA1c by 1.29 points versus 1.34 for Lantus, a difference of just 0.05 percentage points.
Rates of severe hypoglycemia (dangerously low blood sugar) were also equivalent across both trials, regardless of how hypoglycemia was defined or measured. The FDA concluded there was no meaningful difference in effectiveness or safety between the two products.
Why It’s Called a “Follow-On” Instead of a Biosimilar
You may see Basaglar described as a “follow-on biologic” rather than a “biosimilar,” which can be confusing. The distinction is purely regulatory. In the U.S., there are two approval pathways for products that copy an existing biologic. The biosimilar pathway requires a more extensive, stepwise series of studies. Basaglar was approved through a different, slightly less rigorous pathway that still relied on Lantus data but didn’t meet the formal legal definition of “biosimilar.”
At the time of Basaglar’s approval, no insulin products had been licensed under the pathway that would allow a true biosimilar designation, so that route wasn’t available. In practical terms, this regulatory label doesn’t change what Basaglar is or how it works. It simply reflects which paperwork Lilly filed.
Switching Between Basaglar and Lantus
The conversion is one-to-one. If you take 20 units of Lantus at bedtime, you’d take 20 units of Basaglar. No dose adjustment is needed. Both products are U-100, meaning they contain 100 units of insulin glargine per milliliter.
One important caveat: Basaglar does not have an FDA “interchangeable” designation. This means your pharmacist generally cannot swap Lantus for Basaglar (or vice versa) on their own the way they could substitute a generic drug. Your prescriber needs to write the prescription specifically for whichever product you’re using, or your state’s pharmacy laws need to allow the switch. If your insurance formulary prefers one over the other, your doctor can write a new prescription accordingly.
Differences in Delivery Devices
The most noticeable practical difference is how you inject. Lantus comes as both a prefilled SoloStar pen and a multi-dose vial that you draw from with a syringe. Basaglar is only available as a prefilled pen, either the KwikPen or the Tempo Pen. There is no Basaglar vial.
This matters if you use an insulin pump that requires vial-drawn insulin, or if you prefer syringes for any reason. It also matters for dosing flexibility: pens dose in whole units, while syringes allow half-unit increments. If you’re switching from Lantus vials to Basaglar pens, the insulin itself is equivalent, but the mechanics of injecting change.
How Long Basaglar Lasts
Like all insulin glargine products, Basaglar is a long-acting basal insulin. After injection, it provides steady glucose-lowering activity over a full 24 hours with no pronounced peak. In clinical testing, the median time to maximum effect was about 12 hours. This profile is identical to Lantus because the molecule is the same. You inject it once daily, at the same time each day.
Why the Price Difference Exists
Basaglar was introduced specifically to offer a lower-cost alternative to Lantus. Because Lilly could reference Sanofi’s existing safety and efficacy data rather than starting from scratch, their development costs were lower, and that savings is partially passed along. The exact price difference varies by insurance plan and pharmacy, but Basaglar typically costs less than brand-name Lantus. If cost is a factor in your insulin choice, it’s worth comparing your out-of-pocket price for both products through your specific plan.