Toujeo Dose Calculator
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — October 2026
Estimate a starting dose of insulin glargine U-300 — and understand the two things that make Toujeo behave differently from Lantus despite being the same molecule.
💎 Toujeo Starting Dose
Same molecule, different behaviour
Toujeo is insulin glargine — chemically the same as Lantus — formulated at U-300, three times the concentration. That single change alters how it behaves, because a more concentrated depot under the skin has a smaller surface area relative to its volume and therefore dissolves more slowly.
The result is a profile that is flatter and longer: onset over roughly 6 hours, no peak, and duration up to 36 hours against Lantus’s 24. In practice that means more stable overnight coverage and more forgiveness if an injection is late.
| Lantus (U-100) | Toujeo (U-300) | |
|---|---|---|
| Concentration | 100 units/mL | 300 units/mL |
| Onset | 1–2 hours | ~6 hours |
| Duration | ~24 hours | up to 36 hours |
| Time to steady state | 2–3 days | ~5 days |
| Pen capacity | 300 units (3 mL) | 450 units (1.5 mL) |
| In-use window | 28 days | 56 days |
The five-day rule
This is the practical point that catches people out. Toujeo takes around five days to reach full pharmacodynamic steady state, considerably longer than U-100 glargine.
Someone who starts Toujeo and finds fasting glucose still high on day two has not learned that the dose is too low — they have learned that the insulin has not finished arriving. Increasing at that point stacks a change on top of an effect still building, and the low tends to appear several days later when both have landed.
So titrate no more often than every three to four days, as the label states, and expect the first week to look worse than the second on an unchanged dose. The same applies in reverse when reducing.
Switching to or from Toujeo
Because the pen dials in units rather than volume, switching does not require any arithmetic on the patient’s part — you dial the number you are told. But the products are not equivalent unit-for-unit in effect, and the direction matters.
The Toujeo label starts patients on once-daily basal insulin at the same unit dose, and warns that people coming from Lantus usually end up needing a higher daily dose. From twice-daily NPH or detemir, Toujeo starts at 80% of the total daily dose. Going the other way, the Lantus label starts at 80% of the Toujeo dose. Either direction is a prescriber-led change with closer monitoring for the first week or two — which, given the five-day steady state, is exactly how long it takes to see what the change actually did. Other basal options and mealtime tools are covered by our basal insulin calculators.
Toujeo Label Rules: Starting Doses, Pens and Switching
| Situation | Starting Toujeo dose (label, rev. May 2025) |
|---|---|
| Type 1, insulin-naive | 1/3 to 1/2 of the total daily dose; total daily dose 0.2–0.4 units/kg |
| Type 2, insulin-naive | 0.2 units/kg once daily |
| From once-daily basal (incl. Lantus) | Same unit dose; a higher dose is often needed later |
| From twice-daily NPH or detemir | 80% of the total daily dose |
Pens: Toujeo SoloStar holds 450 units, dials in 1-unit steps and gives up to 80 units per injection; Toujeo Max SoloStar holds 900 units, dials in 2-unit steps and gives up to 160 units. The safety test is 3 units on SoloStar and 4 units on Max SoloStar. Either pen is discarded 56 days after first use.
Toujeo Dose Calculator: Limitations & Safety Notes
- Toujeo takes about five days to reach steady state. Titrating more often than every 3–4 days (the label limit) means reacting to an effect that has not fully appeared.
- Switching between Toujeo and any U-100 basal is not a unit-for-unit swap. Dose adjustment and closer monitoring are needed in both directions.
- Never draw Toujeo into a syringe from the pen. At U-300, a syringe marked for U-100 would deliver three times the intended dose.
- A high fasting reading may be dawn phenomenon or rebound rather than insufficient basal. Raising the dose in those cases risks nocturnal hypoglycemia.
- Starting doses are published ranges. Actual requirement is settled by titration under prescriber supervision.
Frequently Asked Questions: Toujeo Dose Calculator
Is Toujeo stronger than Lantus?
It is more concentrated, not more potent per unit. Toujeo is U-300, three times the concentration of Lantus at U-100, which changes how the depot absorbs — flatter and longer — rather than making each unit do more work.
How do I switch from Lantus to Toujeo?
It is a prescriber decision. Because the pen dials in units, you dial the number you are given — but many patients need a somewhat higher unit dose on Toujeo to reach the same fasting control, and the reverse switch usually needs a reduction.
How long does Toujeo take to work?
Onset is over about 6 hours, but the more important figure is that full steady state takes around five days. Judging a dose before then means judging an effect that is still building.
How often should I titrate Toujeo?
No more often than every 3 to 4 days, per the Toujeo label, because the full effect takes about five days to appear. The usual step is 2 units against fasting glucose.
Can I use a syringe with Toujeo?
No. The pen must be used as supplied. At U-300, drawing it into a U-100 syringe would deliver three times the intended dose — a serious overdose risk.
How long does an opened Toujeo pen last?
56 days at room temperature, twice the 28-day window of most U-100 basals. Discarding it at 28 days out of habit throws away four usable weeks.
What is the starting dose of Toujeo?
The Toujeo label starts insulin-naive type 2 patients at 0.2 units per kg once daily, so a 90 kg adult starts at 18 units. In type 1 diabetes, Toujeo covers 1/3 to 1/2 of the total daily dose. Patients already on once-daily basal insulin start at the same unit dose, and those on twice-daily NPH at 80%.
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
- Sanofi. Toujeo (insulin glargine injection) 300 Units/mL — dosing information. Link — concentration, profile and titration
- Endotext / NCBI Bookshelf. Inpatient Diabetes Management. Link — weight-based basal dosing ranges
- Sanofi. Toujeo (insulin glargine injection) 300 Units/mL prescribing information, revised 05/2025. Link
Written by Ryan Mitchell · Last updated: October 2026