Lantus vs Toujeo vs Tresiba: a UK patient comparison of long-acting basal insulins

Lantus, Toujeo and Tresiba are the three long-acting basal insulins UK adults are most often switched between. The molecules are not interchangeable. The pens are not interchangeable. The dosing math is not interchangeable. And the marketing literature for all three is, predictably, clearer about what their drug does well than about where another drug might do something better.

This article collects what the EMA Summaries of Product Characteristics, the head-to-head trial data and the UK BNF prescribing references actually say. It is written for UK adults trying to make sense of a switch, or trying to ask better questions of their diabetes team about one. It is not a recommendation that any reader change their basal insulin. Switches between long-acting insulins involve dose recalculation and titration that needs your prescriber.

The three molecules

Source data: EMA SmPCs. The duration figures are pharmacokinetic profiles in clinical-trial conditions; the practical duration in any individual patient varies.

The key practical point: Lantus and Toujeo are the same molecule at different concentrations. Toujeo is glargine three times more concentrated, which produces a slower release profile. Tresiba is a chemically distinct molecule (degludec) with a different mechanism for sustained release.

Duration: what “ultra-long-acting” buys you

A flat, essentially peakless profile across 24+ hours is the goal of any modern basal insulin, it minimises the risk of overnight hypoglycaemia while providing background insulin coverage between meals. All three products achieve this. The differences are at the margins:

Lantus is the older, established 24-hour basal. Most patients dose it once daily; some dose twice daily for tighter coverage. The clinical evidence base is the largest of the three by a wide margin.

Toujeo is glargine 300 U/mL, which means three units of Toujeo occupy the same injection volume as one unit of Lantus. The slower subcutaneous release this concentration produces extends duration meaningfully, but the trade-off is that initial titration takes longer (about 5 days to steady-state versus 2–3 for Lantus). For patients who already have well-controlled glucose, switching from Lantus to Toujeo typically requires a dose increase of around 10–14% to maintain the same level of control.

Tresiba has the longest duration of the three, with a steady-state half-life of approximately 25 hours producing >42 hours of action. This permits dose-time flexibility: the SmPC explicitly permits a daily injection at any time of day, with at least 8 hours between consecutive doses. For patients whose schedules are irregular, shift workers, frequent travellers, this can be the deciding factor.

Hypoglycaemia rates: the trial evidence

The two head-to-head trials worth knowing about:

SWITCH 1 (Lane et al. 2017) compared Tresiba and Lantus in 501 adults with type 1 diabetes. Across 32 weeks, Tresiba reduced overall symptomatic hypoglycaemia by 11% and nocturnal hypoglycaemia by 36% relative to Lantus, with similar HbA1c outcomes.

BRIGHT (Rosenstock et al. 2018) compared Toujeo and Tresiba in 929 insulin-naive adults with type 2 diabetes. Over 24 weeks, both products produced equivalent HbA1c reduction (~1.6 percentage points), with similar overall hypoglycaemia rates. Toujeo had slightly fewer hypoglycaemic events during the titration phase; Tresiba had slightly fewer in the maintenance phase.

The honest summary: for most patients, all three produce effective basal insulin coverage with low rates of hypoglycaemia. Tresiba has a small advantage on overnight hypoglycaemia in the SWITCH data; Toujeo and Tresiba are functionally equivalent in BRIGHT. Lantus has the largest body of long-term safety evidence simply because it has been on the market the longest.

Pen ergonomics

The clinically relevant difference for adults with hand strength limitations, older patients, patients with arthritis or neuropathy, is that the Tresiba FlexTouch dose button requires substantially less force than the SoloStar mechanism. Lantus and Toujeo both use SoloStar, which has a force profile that scales with the dialled dose. At very high doses (40+ units), depressing the SoloStar requires meaningful thumb pressure; FlexTouch does not.

For high-dose users in particular, the Toujeo DoubleStar is worth knowing about: 900 units per pen at 2-unit increments, which means a patient on 40+ units once daily uses one DoubleStar pen for over three weeks at a time, versus a one-week SoloStar.

Switching: what your prescriber will calculate

This section is informational; do not switch without your team’s involvement.

• Lantus → Toujeo: typical guidance is to start at the same number of units, then titrate up by ~10–14% over the first 2 weeks based on fasting glucose. Toujeo titration is slower than Lantus titration because of the longer time to steady state.
• Lantus → Tresiba: typical guidance is unit-for-unit conversion at the start, with titration adjusted to achieve the same fasting glucose target. Tresiba’s longer duration means rapid up-titration is risky, wait for steady-state (3–4 days) before adjusting.
• Toujeo → Tresiba or Tresiba → Toujeo: not unit-for-unit because of the different concentration / molecule profile. Your prescriber will calculate.

Where each is the better fit

These are general patterns from the trial data and the UK prescribing experience, not individualised recommendations.

Lantus, The default first-line basal in NHS prescribing for many years; large evidence base; well understood. Fine for most patients without specific reason to switch.

Toujeo, Useful for patients who experience persistent overnight hypoglycaemia on Lantus, who need a higher daily dose (the more concentrated formulation is more comfortable to inject in volume), or who prefer the longer-than-24-hour duration.

Tresiba, Useful for patients with irregular schedules where dose-time flexibility matters, for patients with hand strength concerns (FlexTouch is easier to press), or where overnight hypoglycaemia has been a recurring problem.

A note on biosimilars

UK prescribing now includes biosimilar versions of glargine (e.g. Abasaglar, Semglee) which are bioequivalent to Lantus and prescribed unit-for-unit. The molecule, the pharmacokinetics and the practical handling are the same as Lantus; the differences are commercial and regulatory rather than clinical. If your team switches you between branded glargine and a biosimilar, the day-to-day experience should be indistinguishable.

Summary

The three products are not equivalent enough to be interchangeable, and they are not different enough that a patient on a stable, well-controlled regimen has a strong reason to switch. The cases where switching matters are fairly specific: persistent overnight hypoglycaemia, dose-time flexibility constraints, hand strength concerns, or very high daily insulin requirements where a more concentrated or larger-cartridge pen is genuinely more practical.

If you are reading this because you’ve been switched recently and are trying to understand why: ask your diabetes team to walk through the specific reason. The evidence base behind the choice is not opaque, and a five-minute conversation usually clears up the question.