Tresiba (insulin degludec) is an ultra-long-acting basal insulin analog used once daily for type 1 and type 2 diabetes. It has no clinical peak, a duration of action greater than 42 hours, and a uniquely flexible dosing window of 8 to 40 hours between injections. Clinical trials show A1C reductions similar to insulin glargine with about 25 to 30 percent fewer nighttime low blood sugar events. Tresiba is available in U-100 and U-200 FlexTouch pens, and dose is individualized with a prescriber.
What Tresiba Is
Tresiba is the brand name for insulin degludec, made by Novo Nordisk. It is a basal (background) insulin — long-acting insulin designed to cover the steady, between-meal need for insulin, not the rapid surge needed at meals. It is given by subcutaneous injection once daily, usually at the same general time but with much more flexibility than older basal insulins.
Tresiba is FDA-approved for people with type 1 or type 2 diabetes age 1 year and older. It does not replace mealtime (bolus) insulin — most people with type 1 diabetes use Tresiba along with a rapid-acting insulin like Novolog, Humalog, Apidra, or Fiasp.
How Tresiba Works
Insulin degludec is modified from human insulin by removing one amino acid (threonine at position B30) and attaching a fatty acid (hexadecanedioic acid) via a glutamic acid spacer to lysine at B29. This modification allows the insulin molecules to do two things after injection:
- Form long chains of multihexamers (clusters of six insulin molecules linked together) at the injection site
- Slowly release single molecules from the multihexamer chains over many hours, with the released insulin then binding reversibly to albumin in the blood for additional buffering
The result is a slow, steady, near-flat appearance of insulin in the bloodstream. Unlike older basal insulins that have a measurable peak, Tresiba produces a profile so even that pharmacokinetic studies cannot identify a peak — clinicians describe it as truly peakless.
Pharmacokinetics: Onset, Peak, Duration
| Parameter | Insulin Degludec (Tresiba) |
|---|---|
| Onset of action | 30 to 90 minutes |
| Peak | No clinical peak |
| Duration of action | Greater than 42 hours |
| Steady state | Reached after 3 to 4 days of daily dosing |
| Half-life | Approximately 25 hours |
| Concentrations | U-100 (100 units/mL) and U-200 (200 units/mL) |
Who Tresiba Is For
- Adults and children age 1 year and older with type 1 diabetes (combined with mealtime insulin)
- Adults and children age 1 year and older with type 2 diabetes needing basal insulin
- People switching from another basal insulin who experience nocturnal hypoglycemia
- Shift workers, frequent travelers, or anyone with an irregular daily schedule
- People needing high daily basal doses (U-200 reduces injection volume)
How Tresiba Is Used
Tresiba is injected subcutaneously into the abdomen, thigh, or upper arm using a FlexTouch pen. Specifics like starting dose, titration schedule, and target fasting glucose are individualized by the prescriber based on diabetes type, prior insulin use, body weight, A1C, and hypoglycemia history. General principles include:
- Once-daily injection at approximately the same time of day, with flexibility
- Switching from another once-daily basal insulin is typically unit-for-unit, then titrated based on fasting glucose
- Switching from twice-daily basal (such as NPH given twice daily) typically requires a 20 percent dose reduction at start to reduce hypoglycemia risk
- Titration usually adjusts the dose every 3 to 4 days based on fasting glucose readings
- Site rotation reduces injection site reactions and lipohypertrophy
Never self-adjust insulin dose without prescriber guidance. Hypoglycemia and hyperglycemia each have meaningful risks.
Dosing Flexibility
Tresiba is the only basal insulin in the United States with FDA labeling for flexible dose timing. If you miss your usual injection time, you can inject as soon as you remember as long as at least 8 hours have passed since your last dose, and resume your usual schedule afterward. The labeled flexibility window is 8 to 40 hours between consecutive doses.
Practical examples include taking it in the morning on weekdays and in the evening on weekends, adjusting when crossing time zones, or shifting the dose by several hours to fit a new work schedule. This is uniquely useful compared with insulin glargine, which loses some efficacy if dose times drift more than a few hours.
Tresiba vs Other Basal Insulins
| Insulin | Onset | Peak | Duration | Dosing Flexibility |
|---|---|---|---|---|
| Tresiba (degludec) U-100/U-200 | 30 to 90 min | No peak | >42 hours | 8 to 40 hours between doses |
| Toujeo (glargine U-300) | 1 to 6 hours | Near-flat | ~36 hours | Up to 3 hours either side of usual time |
| Lantus / Basaglar / Semglee / Rezvoglar (glargine U-100) | 1 to 3 hours | Near-flat | ~24 hours | Same time daily |
| Levemir (detemir) | 1 to 2 hours | 4 to 9 hours | 12 to 24 hours | Often twice daily |
| NPH (Humulin N / Novolin N) | 1 to 3 hours | 4 to 12 hours | 12 to 18 hours | Twice daily |
Clinical Trial Evidence
The BEGIN clinical trial program — including BEGIN Basal-Bolus Type 1, BEGIN Once Long, BEGIN Low Volume, and several others — established Tresiba’s efficacy and safety profile. Key findings:
- A1C reduction similar to insulin glargine in both type 1 and type 2 diabetes
- Approximately 25 to 30 percent fewer nocturnal hypoglycemia events at similar A1C
- SWITCH 1 (type 1) and SWITCH 2 (type 2) double-blind crossover trials confirmed the hypoglycemia advantage in patients at higher risk for lows
- DEVOTE — a large cardiovascular outcomes trial in type 2 diabetes — confirmed Tresiba is non-inferior to glargine for major adverse cardiovascular events (MACE), with significantly fewer severe hypoglycemia episodes
These results moved Tresiba into mainstream guideline use as a preferred basal option for patients at risk of hypoglycemia, especially nocturnal lows.
Side Effects
- Hypoglycemia (low blood sugar) — most common side effect; nocturnal lows are reduced versus glargine but still possible
- Weight gain (typically a few pounds, usually less than older basal insulins)
- Injection site reactions — redness, itching, small lumps
- Lipodystrophy (lipohypertrophy or lipoatrophy) from repeated injection in the same spot
- Peripheral edema (swelling in the feet or ankles), especially when combined with thiazolidinediones
- Allergic reactions — rare but can include rash, itching, or rare anaphylaxis
- Hypokalemia (low potassium) in certain clinical settings
Combination Products
Insulin degludec is also available in two fixed combination products:
- Ryzodeg 70/30 — degludec plus insulin aspart in a single pen for once- or twice-daily dosing covering both basal and one or two main meals
- Xultophy 100/3.6 — degludec plus liraglutide (a GLP-1 receptor agonist) for type 2 diabetes, combining basal insulin with a daily GLP-1
Cost and Access
- Tresiba FlexTouch pens typically cost around $300 to $500 per month at retail without insurance
- Most commercial and Medicare Part D plans cover Tresiba, sometimes with prior authorization or step therapy from a glargine product
- Novo Nordisk offers patient assistance and a savings card that can lower out-of-pocket cost for eligible patients
- Federal insulin price caps (Medicare Part D at $35/month for covered insulins as of 2023) apply
Storage and Handling
- Unopened pens: refrigerate at 36 to 46 °F (2 to 8 °C) until expiration date
- In use: room temperature up to 86 °F (30 °C) for up to 56 days, then discard
- Do not freeze; do not expose to direct heat or sunlight
- Solution is clear and colorless — discard if cloudy, discolored, or contains particles
- Do not share pens between people, even with a new needle
Related Reading
For a broader overview, see our hub on diabetes treatment options, the head-to-head comparison of insulin degludec vs glargine, and our guide to A1C levels.
The Bottom Line
Tresiba (insulin degludec) is an ultra-long-acting basal insulin with no clinical peak, a duration greater than 42 hours, and uniquely flexible dose timing of 8 to 40 hours apart. Compared with insulin glargine, it produces similar A1C control with about 25 to 30 percent fewer nocturnal hypoglycemia events, and the DEVOTE trial confirmed cardiovascular safety in type 2 diabetes. Side effects include hypoglycemia, weight gain, and injection site reactions. It is available in U-100 and U-200 FlexTouch pens for once-daily dosing. Tresiba may help people with irregular schedules, those needing high doses, or those who have had nighttime lows on other basal insulins — talk to your prescriber to individualize whether and how to start.
