Lantus Dose Calculator
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — October 2026
Estimate a starting dose of insulin glargine U-100 from body weight, with the titration step used to adjust it against fasting glucose.
🌙 Lantus Starting Dose
What Lantus is
Lantus is insulin glargine at U-100 — 100 units per millilitre — and it was the first of the long-acting analogues to give a genuinely flat 24-hour profile. It begins working over 1 to 2 hours, has no pronounced peak, and lasts around 24 hours, which is what makes once-daily basal coverage possible.
That absence of a peak is the clinically important property. NPH, the intermediate insulin it largely replaced for basal use, peaks several hours after injection, which produces a predictable window of hypoglycemia risk. A flat profile removes that window.
| Property | Lantus (glargine U-100) |
|---|---|
| Concentration | U-100 (100 units/mL) |
| Onset | 1–2 hours |
| Peak | None pronounced |
| Duration | ~24 hours |
| Dosing | Once daily, same time each day |
| In-use window | 28 days at room temperature |
Starting and titrating
For an insulin-naive Type 2 patient, basal insulin is conventionally started either at 0.1–0.2 units per kg per day or as a flat 10 units once daily. Both appear in guidance; the fixed start is simpler and the weight-based one is better matched to larger or more insulin-resistant patients.
For Type 1, basal is a share of the total daily dose rather than a standalone calculation. The Lantus label starts it at about one-third of the total daily insulin requirement, with mealtime insulin covering the rest; the ADA describes a split closer to half. Both start from a TDD near 0.5 u/kg/day. Our dose-by-weight calculator works through the full split.
Titration is against fasting glucose, because that is what basal insulin controls. The common algorithm adds 2 units every 3 days until fasting readings reach target; a more cautious version adds 1 unit every 3 to 5 days and is preferable for anyone with hypoglycemia unawareness or a history of nocturnal lows. The three-day interval is not arbitrary — it takes that long for a dose change to show its full effect.
Where it sits against the alternatives
Glargine U-100 is the reference point most other basals are described against, so it is worth knowing how they differ.
| Insulin | Duration | Concentration | Distinguishing feature |
|---|---|---|---|
| Lantus (glargine) | ~24 h | U-100 | The flat-profile baseline |
| Toujeo (glargine) | up to 36 h | U-300 | Same molecule, three times concentrated, flatter still |
| Tresiba (degludec) | up to 42 h | U-100 / U-200 | Longest duration; flexible injection timing |
| Levemir (detemir, discontinued in the US end-2024) | ~12–24 h | U-100 | Sometimes twice daily; 42-day in-use window |
| NPH | ~12–18 h | U-100 | Has a peak; usually twice daily |
Biosimilar glargines — Basaglar, Semglee, Rezvoglar — are U-100 glargine like Lantus and are dosed on the same basis, though switching is still a prescriber decision. Mealtime and correction tools that pair with glargine are in our basal and bolus insulin calculators.
Lantus Dosage Chart: Label Starting Doses and Switching
The current Lantus prescribing information (revised May 2025) sets these starting points — use the table below as a Lantus starting-dose chart for the most common situations:
| Situation | Starting Lantus dose (label) |
|---|---|
| Type 1 diabetes | About one-third of the total daily insulin requirement, plus mealtime insulin |
| Type 2, not on insulin | 0.2 units/kg or up to 10 units once daily |
| From once-daily Toujeo | 80% of the Toujeo dose |
| From once-daily NPH | Same dose as the NPH |
| From twice-daily NPH | 80% of the total daily NPH dose |
Lantus is injected once a day at any time, but at the same time every day. It comes as a 10 mL vial and a 3 mL SoloStar pen that dials in 1-unit steps, and it must never be mixed or diluted with another insulin.
Lantus Dose Calculator: Limitations & Safety Notes
- Starting doses are published ranges, not prescriptions. Actual requirement emerges over weeks of titration against fasting glucose.
- Basal insulin does not cover meals. Persistent post-meal highs indicate a mealtime insulin problem, not a basal one.
- A high fasting reading is not always insufficient basal — dawn phenomenon and post-hypoglycemic rebound look identical on a morning meter, and raising basal in either case risks nocturnal hypoglycemia.
- Reduced kidney function lowers insulin requirement because injected insulin is cleared renally.
- Switching between basal insulins follows each label: Toujeo to Lantus starts at 80% of the Toujeo dose, and twice-daily NPH to Lantus at 80% of the total NPH dose. Every switch is a prescriber decision with closer glucose checks.
Frequently Asked Questions: Lantus Dose Calculator
How do I calculate my Lantus dose?
For an insulin-naive Type 2 patient the Lantus label starts at 0.2 units per kg or up to 10 units once daily; the ADA range is 0.1–0.2 units per kg. In Type 1, the label starts Lantus at about one-third of the total daily dose. Both are starting points that get titrated against fasting glucose.
When should I take Lantus?
Once daily at the same time each day. Which time matters less than consistency, because the profile is flat across 24 hours — but moving the injection around undermines that.
How quickly can I increase my Lantus dose?
The common algorithm is 2 units every 3 days until fasting glucose reaches target, or 1 unit every 3–5 days if you are prone to lows. Faster than that outruns the time a change needs to show its full effect.
Is Lantus the same as Toujeo?
Same molecule, different concentration. Toujeo is glargine at U-300 — three times as concentrated — which changes the absorption profile, making it flatter and longer-acting. They are not interchangeable unit-for-unit.
Can I mix Lantus with other insulins in the same syringe?
No. Glargine must not be mixed or diluted with any other insulin; doing so alters its action profile. It is given as a separate injection.
How long does an opened Lantus pen last?
28 days at room temperature below 86°F, after which it should be discarded even if insulin remains. Our expiration date calculator works out the exact date.
How much Lantus should a type 1 diabetic take?
The Lantus label starts type 1 patients at about one-third of their total daily insulin requirement, with rapid-acting insulin at meals covering the rest. For a total daily dose of 36 units, that is about 12 units of Lantus once daily. The dose is then titrated against fasting glucose with your care team.
Sources
- American Diabetes Association. 9. Pharmacologic Approaches to Glycemic Treatment: Standards of Care in Diabetes — 2026. Diabetes Care. 2026;49(Suppl 1):S183. Link — basal initiation and titration principles
- Endotext / NCBI Bookshelf. Inpatient Diabetes Management. Link — weight-based basal dosing ranges
- Novo Nordisk / manufacturer storage and stability references for basal insulin analogues. Link — in-use windows for comparison
- Sanofi. Lantus (insulin glargine injection) prescribing information, revised 05/2025. Link
Written by Ryan Mitchell · Last updated: October 2026