Lantus Dose Calculator
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 — commonly around half of a TDD that itself starts 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) | ~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.
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.
- Glargine products are not interchangeable unit-for-unit with degludec or with glargine U-300. Switching requires a dose review.
Frequently Asked Questions
How do I calculate my Lantus dose?
For an insulin-naive Type 2 patient the usual start is 0.1–0.2 units per kg per day, or a flat 10 units once daily. In Type 1, basal is roughly half of a total daily dose that itself starts near 0.5 u/kg. 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.
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
Last reviewed: July 2026