Semglee and Rezvoglar (Insulin Glargine Biosimilars): How These Long-Acting Insulins Work and When Telehealth Is Enough

Last updated: August 19, 2026

Semglee (insulin glargine-yfgn) and Rezvoglar (insulin glargine-aglr) are long-acting (basal) insulin glargine products. People also search “semglee insulin,” “semglee pen,” “rezvoglar kwikpen,” and “insulin glargine biosimilar.” Those names point to U-100 biosimilars of Lantus, not to Toujeo (insulin glargine U-300), not to Basaglar as a follow-on brand, and not to meal-time pens such as Humalog or NovoLog. They are not a treatment for diabetic ketoacidosis. Do not treat a pharmacy switch as a reason to change your own units without a clinician check.

This guide covers how Semglee and Rezvoglar are usually injected, how a vial differs from a KwikPen, what FDA interchangeability with Lantus means at the counter, and when a video visit is enough versus when you need labs or the ER. It is educational. It is not a diagnosis or a promise that any specific insulin will be prescribed.

Want a licensed clinician to review basal insulin or an A1C? Klarity Health has 2,000+ licensed providers. Many visits happen online. See online prescription options or browse conditions.

TLDR

• DailyMed lists Semglee (insulin glargine-yfgn) as a long-acting human insulin analog to improve glycemic control in adult and pediatric patients with diabetes mellitus. It is biosimilar to Lantus. It is not recommended for diabetic ketoacidosis. Presentations are 100 units/mL (U-100): a 10 mL multiple-dose vial and a 3 mL single-patient-use prefilled pen (DailyMed Semglee).
• DailyMed lists Rezvoglar (insulin glargine-aglr) as a long-acting human insulin analog for the same indication. It is biosimilar to Lantus. It is supplied as a 3 mL KwikPen only (100 units/mL). The pen can inject 1 to 80 units in one shot. Needles are sold separately (DailyMed Rezvoglar KwikPen).
• In November 2022 the FDA approved Rezvoglar as the second interchangeable biosimilar insulin product to Lantus. An interchangeable product may be substituted for Lantus at the pharmacy without a new prescription, subject to state pharmacy law. Semglee was the first interchangeable insulin glargine product to Lantus (FDA interchangeability coverage).
• Starting doses on both labels match the Lantus pattern: type 1, about one-third of total daily insulin as the basal, with short-acting insulin for meals; type 2 not already on insulin, 0.2 units/kg or up to 10 units once daily. Inject once a day at the same time every day. Do not mix. Do not use in a pump. Do not inject into a vein.
• MedlinePlus groups Lantus, Basaglar, Semglee, Rezvoglar, and Toujeo as insulin glargine products. The products are highly similar. They are not always the same carton at the counter. Always check the name on the pen or vial (MedlinePlus insulin glargine).
• Mayo Clinic describes insulin glargine as a long-acting insulin that works slowly over about 24 hours. Inject it under the skin of the abdomen, upper arm, or thigh. Rotate sites (Mayo Clinic insulin glargine).
• In-use Rezvoglar KwikPen: 28 days at room temperature only; do not put the opened pen back in the fridge. Unused refrigerated pens last until the labeled expiration date. Do not freeze. Semglee unused stock is refrigerated; opened vials can stay refrigerated or at room temperature for 28 days; opened pens stay at room temperature for 28 days (MedlinePlus storage).
• Typical home glucose targets many adults use: 80 to 130 mg/dL before meals and under 180 mg/dL two hours after a meal starts. A reading under 70 mg/dL is low. If you are sick and a reading is 240 mg/dL or higher, check ketones (CDC manage blood sugar).
• Medicare covers many telehealth visits from home anywhere in the U.S. through December 31, 2027 (HHS telehealth policy). Seizure, loss of consciousness, chest pain, or blood sugar that will not come up is 911, not a video visit.

What Semglee and Rezvoglar are trying to fix

Type 1 diabetes means the pancreas makes little or no insulin. Type 2 diabetes means the body resists insulin and often does not make enough of it. Glucose stays in the blood. Over years that raises the chance of heart disease, stroke, kidney disease, nerve damage, and eye disease. NIDDK notes some people with type 2 diabetes can control glucose with food, activity, sleep, and weight change. Many still need pills or insulin. Over time you may need more than one medicine (NIDDK insulin and medicines).

Insulin glargine replaces background insulin. MedlinePlus says it moves sugar from the blood into tissues and slows the liver from making more sugar. It does not cover the spike right after a meal. That is why type 1 regimens add a short-acting insulin at meals, and why some type 2 regimens still use meal-time insulin or an oral class.

A biosimilar is not a generic tablet. DailyMed defines it as a biological product approved because it is highly similar to an FDA-approved reference product and there are no clinically meaningful differences. For Semglee and Rezvoglar the reference is Lantus. Interchangeable status is an extra FDA finding. It means a pharmacist may substitute the biosimilar for Lantus when state law allows, without calling the prescriber first. Your plan may still prefer one brand. Coverage varies by plan. Verify benefits before you assume the carton will stay the same month to month.

Typical home targets the CDC lists for many adults:

• Before a meal: 80 to 130 mg/dL
• Two hours after the start of a meal: under 180 mg/dL

Blood sugar under 70 mg/dL is low. If you are sick and a reading is 240 mg/dL or higher, check ketones. High ketones can signal diabetic ketoacidosis, which is an emergency. Semglee and Rezvoglar are not the insulins used to treat DKA. Both labels say they are not recommended for that use.

Related Klarity guides: Lantus (insulin glargine U-100), Toujeo (insulin glargine U-300), Tresiba (insulin degludec), NPH (Humulin N, Novolin N), and type 2 diabetes medication.

How Semglee and Rezvoglar are usually taken

Both products are clear, colorless U-100 solutions injected under the skin. DailyMed and MedlinePlus adult directions:

• Once a day, at the same time every day. The labels allow any time of day if that time stays consistent.
• Sites: abdomen, thigh, or upper arm. Rotate within the area. Do not inject into pits, lumps, scars, or damaged skin.
• Do not dilute. Do not mix with any other insulin or liquid. Do not put either product in an insulin pump. Do not inject into a vein.
• Never share a pen, needle, or syringe, even if you change the needle.
• Do not use a syringe to pull insulin out of a Rezvoglar KwikPen.
• Prime the KwikPen (safety test of 2 units) before each injection. Hold the dose knob in and count to 5 after the window shows 0.

Type 1 start on both labels: about one-third of total daily insulin as Semglee or Rezvoglar; short-acting insulin covers the rest at meals. Type 2 not already on insulin: 0.2 units/kg or up to 10 units once daily. A clinician then titrates from home glucose logs. Do not copy a neighbor’s units.

When a pharmacy substitutes Semglee or Rezvoglar for Lantus, the unit dose often stays the same at first because all three are U-100 glargine. Still check the carton. Toujeo is a different concentration. Mixing those pens is a dosing error. DailyMed warns that changes in manufacturer, type, or injection method can raise or drop glucose. Increase checks for several days after any switch.

Semglee versus Rezvoglar versus Lantus and Toujeo

• Molecule class: All four names are insulin glargine. Semglee and Rezvoglar are biosimilars of Lantus. Toujeo is concentrated U-300 glargine, not a Lantus interchangeable.
• Devices: Semglee comes as a 10 mL vial and a 3 mL pen. Rezvoglar is KwikPen only (3 mL, 1 to 80 units). Lantus has a vial and SoloStar. Toujeo uses SoloStar and Max SoloStar pens at U-300.
• Pharmacy substitution: Interchangeable status applies to Lantus, not automatically to Basaglar or Toujeo. State law still governs what the pharmacist can swap.
• Storage after opening: Opened pens for these U-100 products typically last 28 days at room temperature. Unused refrigerated stock lasts until the expiration date if it never freezes.

Insurance may prefer one interchangeable product over another. A plan may also prefer a follow-on brand such as Basaglar that is not interchangeable. Ask the pharmacy which name they will fill before you leave empty-handed. Klarity clinicians can review logs and write a clinically appropriate basal insulin. They cannot promise a specific brand will stay on your formulary.

Who should not use these pens

Do not use Semglee or Rezvoglar during a low-blood-sugar episode or if you are allergic to insulin glargine or an excipient. Combining insulin with a TZD (pioglitazone, rosiglitazone) can cause fluid retention and heart failure. Watch for sudden weight gain, ankle swelling, or shortness of breath. All insulins can lower potassium. Severe allergy (whole-body rash, trouble breathing, swelling of the face or throat) is an emergency. Stop the product and get care.

Side effects people actually notice

Hypoglycemia is the most common insulin side effect. DailyMed notes the long action of glargine can delay recovery from a low. Other common reactions: injection-site redness, lipodystrophy, itch, rash, edema, and weight gain. Check the label before every shot so you do not inject the wrong insulin.

When telehealth is enough, and when it is not

A video visit can often review fasting and bedtime logs, discuss a pharmacy substitution, adjust a basal dose in small steps, order an A1C, and talk through missed-dose rules. Medicare currently covers many telehealth visits from home through December 31, 2027. Coverage for commercial plans still varies. Verify benefits before you book.

Go to the ER or call 911 for seizure, loss of consciousness, chest pain, severe allergic reaction, or blood sugar that will not rise with your usual treatment. High ketones with vomiting or rapid breathing is not a “wait for the next slot” problem. Pump users who lose basal coverage (these products are not for pumps) need a backup injection plan.

How Klarity Health can help

Klarity Health has 2,000+ licensed providers. Many visits happen online. A clinician can review whether a long-acting insulin still fits your logs, whether a meal-time insulin or an oral class should change with it, and when labs or in-person care are safer. Prescriptions, if appropriate, go to a pharmacy you choose. No article can promise a specific brand or that insurance will pay.

Ready to talk through basal insulin? See online prescription options or browse conditions.

FAQ

Are Semglee and Rezvoglar the same as Lantus?

They are insulin glargine biosimilars of Lantus. FDA interchangeable status means a pharmacist may substitute them for Lantus when state law allows. Check the carton. Do not assume every “glargine” pen is U-100 Lantus-class. Toujeo is U-300.

Can I switch from Lantus to Semglee on my own?

Do not change brands or units without a clinician. A pharmacy may legally substitute an interchangeable product. Still increase glucose checks for several days and confirm the device (vial versus KwikPen versus SoloStar) matches what you know how to use.

Does insurance cover Semglee or Rezvoglar?

Coverage varies by plan, deductible, and formulary. A plan may prefer one interchangeable product, a follow-on brand, or the reference Lantus. Verify benefits before you count on a specific name.

Can I use these in a pump?

No. DailyMed says do not use Semglee or Rezvoglar in an insulin pump and do not inject them into a vein.

Disclaimer

This article is for education. It is not medical advice, a diagnosis, or a guarantee of insurance coverage. Coverage and pharmacy substitution rules vary by plan and state. Confirm benefits and the product name on the carton before you inject. Talk with a licensed clinician before you change any insulin.