Tresiba Dose Calculator
Estimate a starting dose of insulin degludec, and understand the property that sets it apart: a duration long enough that injection timing can vary day to day.
⌛ Tresiba Starting Dose
The longest-acting basal
Insulin degludec forms soluble multi-hexamer chains after injection that release monomers slowly and steadily. The practical result is a duration of action of up to 42 hours with minimal peak — substantially longer than glargine U-100 at around 24 hours.
Because each dose is still working when the next one is given, the level in the body is the average of recent doses rather than a series of separate curves. That produces unusually stable day-to-day coverage, and it is the basis of the property Tresiba is best known for.
| Property | Tresiba (degludec) |
|---|---|
| Concentrations | U-100 and U-200 |
| Peak | Minimal |
| Duration | up to 42 hours |
| Steady state | ~3 days |
| Dosing | Once daily, timing may vary |
| In-use window | 56 days at room temperature |
Flexible timing — what it does and does not mean
Because the duration exceeds 24 hours by a wide margin, degludec tolerates variation in injection time in a way shorter basals do not. For someone doing shift work, travelling across time zones, or simply living an irregular schedule, that removes a persistent source of instability.
What it does not mean is that timing is irrelevant. The guidance is that doses should be spaced at least 8 hours apart, and a broadly consistent routine is still better than a chaotic one. Flexibility is insurance against real life, not a licence to inject whenever.
It also does not mean doses can be skipped. A missed dose still leaves a gap; the long tail softens it rather than removing it.
U-100 versus U-200
Tresiba is supplied in two concentrations, and the distinction confuses people because it changes nothing about how you dial the dose. Both pens are marked in units and both deliver the units you select. What differs is volume: the U-200 pen delivers the same number of units in half the liquid.
That matters for anyone on large doses, where a U-100 injection volume becomes uncomfortable, and it means a U-200 pen lasts twice as long at the same daily dose. There is no dose conversion when switching between them — the same unit number is the same unit number.
The one absolute rule: never draw degludec from a pen into a syringe. A U-200 pen drawn into a U-100 syringe would deliver twice the intended dose.
Limitations & Safety Notes
- Doses should be at least 8 hours apart. Flexible timing is tolerance for an irregular schedule, not permission to inject at random.
- Steady state takes around 3 days and the tail extends to 42 hours, so dose changes take time to show their full effect. Titrate no faster than every 3 to 4 days.
- Never draw Tresiba from a pen into a syringe. A U-200 pen in a U-100 syringe delivers double the intended dose.
- Degludec is not interchangeable unit-for-unit with glargine. Switching requires a prescriber-led dose review.
- A missed dose still leaves a gap in coverage; the long duration reduces the consequence rather than eliminating it.
Frequently Asked Questions
How long does Tresiba last?
Up to 42 hours, which is the longest of the commonly used basal insulins. Because each dose is still active when the next is given, blood levels reflect an average of recent doses rather than individual peaks.
Can I take Tresiba at different times each day?
Within limits, yes — that flexibility is its distinguishing feature. Doses should still be at least 8 hours apart, and a broadly consistent routine remains preferable.
What is the difference between Tresiba U-100 and U-200?
Only the volume. Both dial in units and deliver the units you select; the U-200 pen delivers them in half the liquid, which suits large doses and makes a pen last twice as long. There is no dose conversion between them.
How do I switch from Lantus to Tresiba?
It is a prescriber decision requiring a dose review — the two are not interchangeable unit-for-unit. Expect closer monitoring for the first week while the longer profile establishes.
How often should I adjust my Tresiba dose?
No more than every 3 to 4 days against fasting glucose, typically in 2-unit steps. Steady state takes about three days, so faster adjustment reacts to an incomplete picture.
How long does an opened Tresiba pen last?
56 days at room temperature, double the 28-day window that applies to most U-100 basals.
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
- Novo Nordisk. Storage and stability — insulins. Link — Tresiba U-100/U-200 in-use window
- Endotext / NCBI Bookshelf. Inpatient Diabetes Management. Link — weight-based basal dosing ranges
Last reviewed: July 2026