Lantus (Insulin Glargine): How This Long-Acting Insulin Works and When Telehealth Is Enough

Last updated: August 18, 2026

Lantus is a brand name for insulin glargine, a long-acting (basal) insulin analog. Clinicians use it to improve blood sugar control in people with type 1 diabetes and in adults with type 2 diabetes who need insulin. People also search “Lantus insulin,” “insulin glargine,” “Basaglar,” “Semglee,” and “Lantus SoloStar pen.” Those names point to the same molecule class. The products are not automatically interchangeable at the pharmacy counter without a clinician and pharmacist check. Lantus is not a meal-time insulin, not an insulin pump cartridge, and not a treatment for diabetic ketoacidosis.

This guide covers how Lantus is usually injected, how U-100 vials and SoloStar pens differ from concentrated Toujeo, who should not use it, common side effects, 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

• Insulin glargine (Lantus) is a once-daily long-acting insulin for type 1 and type 2 diabetes. In type 1 diabetes it must be paired with a short-acting insulin. It is not given in a vein or an insulin pump (MedlinePlus insulin glargine; FDA Lantus label).
• 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. Do not inject into a vein or muscle (Mayo Clinic insulin glargine).
• FDA label: inject once daily at any time of day, but at the same time every day. For type 2 adults not already on insulin, the recommended start is 0.2 units/kg or up to 10 units once daily. Switching from once-daily NPH uses the same unit dose. Switching from twice-daily NPH starts at 80% of the total daily NPH dose. Do not dilute or mix Lantus with any other insulin.
• Lantus is U-100 (100 units/mL) in a 10 mL vial or SoloStar pen. Toujeo is a different, more concentrated insulin glargine product (U-300). Do not treat the click count on one pen as the same as another brand or concentration.
• Do not use Lantus during a low-blood-sugar episode or if you are allergic to insulin glargine. Never share a pen or needle. Combining insulin with a TZD (pioglitazone, rosiglitazone) can cause fluid retention and heart failure.
• 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 (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 Lantus is 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.

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. Lantus is not the insulin used to treat DKA.

Related Klarity guides: Tresiba (insulin degludec), type 2 diabetes medication, SGLT2 inhibitors, sulfonylureas, DPP-4 inhibitors, TZDs, meal-time diabetes pills, and bromocriptine (Cycloset).

How Lantus is usually taken

Lantus is a clear, colorless solution injected under the skin. MedlinePlus and FDA adult directions:

• Once a day, at the same time every day. The FDA label allows any time of day as long as that time stays consistent. Mayo Clinic often describes bedtime dosing because the effect lasts about 24 hours.
• Sites: abdomen, upper arm, or thigh. Rotate within the same region. Skip areas that are lumpy, scarred, bruised, or hard.
• Insulin-naive type 2 adults: the FDA label lists 0.2 units/kg or up to 10 units once daily as a common start. The clinician then titrates against fasting glucose and A1C.
• Type 1: Lantus is only part of the plan. You still need a short-acting insulin for meals. The starting basal dose is a share of total daily insulin, set by the clinician.
• NPH switch: once-daily NPH to once-daily Lantus uses the same unit number. Twice-daily NPH to once-daily Lantus starts at 80% of the total daily NPH dose, then adjusts.

Do not mix Lantus in the same syringe with another insulin. Do not dilute it. Do not put it in an insulin pump. Do not inject it into a vein. Check the label every time. The liquid should stay clear. Cloudiness, color, or particles means you throw that pen or vial away.

Never share a pen, cartridge, or needle. Mayo Clinic is blunt: one pen is for one person. Sharing can pass hepatitis, HIV, or other bloodborne infections.

Lantus, Basaglar, Semglee, and Toujeo

MedlinePlus lists several insulin glargine products: Lantus, Basaglar, Semglee (insulin glargine-yfgn), Rezvoglar (insulin glargine-aglr), and Toujeo. Biosimilars are highly similar to the reference product and work the same way in the body. That does not mean every plan, pharmacy, or device treats them as automatic substitutes.

Concentration is the trap people miss. Lantus, Basaglar, and Semglee are U-100. Toujeo is a more concentrated U-300 insulin glargine. The dose window on a pen already shows insulin units, but you still cannot treat one brand’s pen as another brand’s pen. If a clinician switches you from Toujeo to a U-100 product, the starting U-100 dose is often lower than the Toujeo unit number. That conversion belongs to the prescriber, not a coupon page.

Soliqua is a different product: insulin glargine plus lixisenatide in one pen. It is not a Lantus substitute and is not the focus of this article.

Who should not use Lantus

Do not inject Lantus during hypoglycemia. Do not use it if you had a serious allergy to insulin glargine. Tell the clinician about heart failure, low potassium, kidney or liver disease, vision problems, and diabetic nerve damage. Mention every medicine, including pioglitazone and rosiglitazone. Insulin plus a TZD can cause fluid retention and heart failure.

Alcohol can drop or swing blood sugar. Illness, extra activity, skipped meals, and travel across time zones all change how much insulin you need. Ask for a written sick-day plan before you need it.

Mayo Clinic notes Lantus safety data in children 6 and older with type 1 diabetes. Safety in younger children with type 1, and in children with type 2, is not established the same way. Pregnancy and breastfeeding decisions belong to the obstetric and diabetes team. Insulin is often used in pregnancy when diet and activity are not enough; that is a specialist call, not a self-start.

Side effects and storage

The expected effect is lower blood sugar. Too much insulin, too little food, or extra exercise can push you under 70 mg/dL. Mild lows often respond to 15 grams of fast carbohydrate and a recheck in 15 minutes. Confusion, seizure, or collapse is 911. Overdose also goes through poison control at 1-800-222-1222.

Common local effects: redness, swelling, itch, or a change in fat under the skin at the injection site. Rotate sites so you do not keep hitting the same square inch.

Serious signs that need urgent care: whole-body rash or hives, wheezing, trouble swallowing, swelling of the face or tongue, sudden weight gain, ankle swelling, or new shortness of breath.

Unopened vials and pens stay in the refrigerator. Do not freeze. An in-use Lantus vial can sit in the fridge or at room temperature and should be discarded after 28 days. An in-use SoloStar pen stays at room temperature and is discarded after 28 days. Mayo Clinic notes opened Toujeo pens last longer (56 days). That extra window does not apply to Lantus.

When a video visit is enough

A licensed clinician can often review fasting logs, A1C, current pens, and hypoglycemia history on video. That visit may be enough to continue a stable Lantus dose, adjust a few units, or decide that an oral class such as metformin or an SGLT2 inhibitor still belongs in the plan. Klarity Health’s online prescription visit is one way to have that conversation. Coverage varies by plan. Verify benefits before you book.

Medicare patients can receive many non-behavioral telehealth visits from home, with no geographic originating-site limit, through December 31, 2027. That window does not replace an ER when you cannot stay awake, cannot keep fluids down, or have high ketones.

Go in person, or to urgent care or the ER, when:

• Blood sugar stays under 70 mg/dL after treatment, or you lose consciousness
• You are sick and glucose is 240 mg/dL or higher with high ketones
• You have chest pain, severe shortness of breath, or one-sided weakness
• You cannot keep food or fluids down
• You need a new diagnosis of type 1 diabetes or suspected DKA

Insurance, cost, and what “covered” actually means

A plan may list Lantus, a biosimilar, or another basal insulin on formulary. Tier, prior authorization, and preferred pen versus vial rules vary. A clinician cannot promise that your specific policy will pay for a brand. Ask the plan for the current insulin list and the preferred basal product. Manufacturer coupons sometimes help commercially insured patients. They usually do not apply to Medicare or Medicaid.

Disclaimer: Insurance coverage varies by plan and is not guaranteed. This article does not confirm that any insurer will pay for Lantus, Basaglar, Semglee, Toujeo, or a telehealth visit. Verify benefits with your plan before you book care or fill a prescription.

Questions a clinician will ask

• What is your most recent A1C, and what do fasting readings look like for the last two weeks?
• Which pen or vial do you actually have at home, including the concentration on the box?
• How many lows have you had, and did anyone else have to help you?
• Which pills or other injectables do you take, including a TZD or a sulfonylurea?
• Are you pregnant, planning pregnancy, or breastfeeding?

Bring the pen or a clear photo of the box. Brand mix-ups are a common reason a dose looks “wrong.”

FAQ

Is Lantus the same as insulin glargine?

Lantus is one brand of insulin glargine U-100. Basaglar and Semglee are related U-100 products. Toujeo is insulin glargine at a higher concentration. A pharmacist should confirm which product your prescription and your plan allow.

Can I take Lantus twice a day?

The labeled schedule is once daily at the same time. Some clinicians split a dose in selected cases. That is off the standard label path and needs a specific reason, not a search-result guess.

Can I get a Lantus prescription online?

A licensed clinician may continue or adjust basal insulin after a video visit if your history, glucose data, and exam needs support that plan. New severe hyperglycemia, suspected type 1, or DKA is not an online-only problem. See online prescription options.

What if I miss a dose?

MedlinePlus tells you to get written instructions from your own clinician before the first missed dose. Do not double the next injection to “catch up” unless that clinician told you to.

Bottom line

Lantus (insulin glargine) is a once-daily basal insulin. It covers background glucose. It does not replace meal-time insulin in type 1 diabetes, and it does not treat DKA. Use the same time every day, rotate sites, and never mix it in a syringe or a pump. A telehealth visit can often review logs and refill a stable regimen. Emergencies and new ketones still belong in an ER.

Ready to talk through basal insulin? Klarity Health has 2,000+ licensed providers. See if an online prescription visit may fit or browse conditions.