Insulin detemir
detemir, NN304, LysB29(Nε-tetradecanoyl) des(B30) human insulin, myristoylated insulin analogue
Insulin detemir is a basal insulin analogue that works by binding reversibly to albumin in the blood and in subcutaneous tissue, creating a circulating buffer that slows and smooths its action. It was the first acylated insulin analogue and is notable for causing less weight gain than other basal insulins. The manufacturer discontinued it in the United States at the end of 2024, so it is now of largely historical and comparative interest in that market.
Mechanism
Insulin detemir is human insulin with the C-terminal threonine at B30 removed and a fourteen-carbon saturated fatty acid (myristic acid) attached directly to the epsilon-amino group of lysine B29. Unlike degludec, there is no glutamyl spacer and the fatty acid is a mono-acid rather than a diacid, which gives weaker albumin affinity and a correspondingly shorter duration. Protraction arises from two mechanisms working together. In the subcutaneous depot the fatty acid promotes self-association into hexamers and dihexamers, slowing dissolution and diffusion into the circulation; and, once absorbed, more than 98% of the drug is bound reversibly to serum albumin through the myristoyl chain, so free insulin concentrations rise and fall slowly and are buffered against fluctuations in absorption.
Albumin binding also has a distributional consequence that may explain detemir's most reproducible clinical peculiarity, its lesser weight gain. Because albumin-bound insulin crosses the fenestrated hepatic sinusoidal endothelium more readily than the continuous endothelium of peripheral tissue, detemir is thought to act preferentially on the liver relative to muscle and fat, which reduces peripheral lipogenesis; a central satiety effect at the hypothalamus has also been proposed. Neither explanation is definitively established. At the receptor level detemir has substantially lower molar potency than human insulin, so the 100 units/mL product contains four times the molar concentration (2,400 nmol/mL rather than 600 nmol/mL), which is why detemir unit requirements often look higher than for other basal insulins. Its IGF-1 receptor affinity is proportionately lower than its insulin receptor affinity, giving a favourable metabolic-to-mitogenic ratio. Downstream signalling is conventional: receptor autophosphorylation, IRS/PI3K/AKT activation, GLUT4 translocation, and suppression of hepatic gluconeogenesis and glycogenolysis.
What the research shows
Detemir's randomised evidence is consistent on three points. Against isophane insulin it achieves broadly the same HbA1c with roughly half the hypoglycaemia and substantially less nocturnal hypoglycaemia. Against glargine it is non-inferior for HbA1c with comparable hypoglycaemia. And across essentially every trial in which it has been studied, it produces less weight gain than any comparator basal insulin, typically one to two kilograms less over six to twelve months, and in the STEADINESS trial no weight gain at all where isophane insulin produced a rise. That weight signal is the most distinctive and reproducible finding in the detemir literature, and it is one of the few places where a basal insulin analogue offers something that a cheaper alternative genuinely does not.
The counterweight is duration. Detemir's albumin affinity is weaker than degludec's diacid-mediated binding, and its duration is dose-dependent and frequently shorter than 24 hours at ordinary doses. In the 52-week Rosenstock comparison against glargine, roughly half the detemir arm needed twice-daily injection to reach target, which erodes the convenience case and increases total insulin exposure. The 4-T trial provides the most useful long-term context: over three years, starting with basal detemir gave broadly equivalent HbA1c to more complex regimens once intensification was allowed, with roughly a third of the hypoglycaemia and about half the weight gain, which shaped a generation of type 2 diabetes guidelines. Detemir has no dedicated cardiovascular outcome trial and no evidence that it reduces long-term complications relative to isophane insulin. Its commercial withdrawal from the US market at the end of 2024 was a manufacturing and formulary decision rather than a safety one, but it means that for many patients detemir is now a comparator in the literature rather than a treatment option.
Evidence assessment
High-quality evidence
Licensed in the European Union in 2004 and by the FDA in 2005 on the basis of multiple adequately powered randomised treat-to-target trials in both type 1 and type 2 diabetes, and studied as the basal arm of the 708-participant 4-T trial with three years of follow-up. The evidence is regulator-grade and replicated. It is worth being precise about what it establishes: HbA1c broadly equivalent to isophane insulin and glargine (with a small pooled advantage over isophane insulin in one type 1 trial), less nocturnal hypoglycaemia than isophane insulin, and consistently less weight gain, not materially better glycaemic control or better long-term outcomes.
Tiers are applied consistently across the library and re-checked when new trials read out. Read the grading method.
Key studies
Insulin detemir offers improved glycemic control compared with NPH insulin in people with type 1 diabetes: a randomized clinical trial Preclinical only
Detemir gave lower clinic fasting plasma glucose and lower self-measured prebreakfast glucose than isophane insulin, with reduced minor hypoglycaemia and about 53% less nocturnal hypoglycaemia in one comparison. Individual detemir arms did not differ significantly from isophane insulin on HbA1c, though the pooled detemir groups did. Body weight rose in the isophane group but not with detemir, the first clear demonstration of detemir's weight-neutral signature.
A 26-week, randomized, parallel, treat-to-target trial comparing insulin detemir with NPH insulin as add-on therapy to oral glucose-lowering drugs in insulin-naive people with type 2 diabetes Preclinical only
HbA1c was equivalent between detemir and isophane insulin. Risk of hypoglycaemia was substantially lower with detemir (roughly 47% lower for all hypoglycaemia and around 55% lower for nocturnal episodes), and weight gain was less than half that seen with isophane insulin (approximately 1.2 kg versus 2.8 kg).
A randomised, 52-week, treat-to-target trial comparing insulin detemir with insulin glargine when administered as add-on to glucose-lowering drugs in insulin-naive people with type 2 diabetes Preclinical only
Detemir was non-inferior to glargine for HbA1c, with both arms achieving reductions of about 1.5 percentage points and similar hypoglycaemia rates. Weight gain was smaller with detemir (approximately 3.0 kg versus 3.9 kg). Roughly half the detemir group required twice-daily dosing to reach target, the practical trade-off for detemir's shorter duration.
Addition of biphasic, prandial, or basal insulin to oral therapy in type 2 diabetes Preclinical only
At one year, basal detemir gave the highest HbA1c of the three strategies (approximately 7.6% versus 7.3% with biphasic aspart and 7.2% with prandial aspart) but the lowest rates of hypoglycaemia and the least weight gain. An honest demonstration that basal-only initiation is gentler but less potent in the short term.
Three-year efficacy of complex insulin regimens in type 2 diabetes Preclinical only
By three years the initial HbA1c gap had closed (approximately 7.1%, 6.8% and 6.9% for the biphasic, prandial and basal detemir strategies), but the basal detemir strategy retained clear advantages: hypoglycaemia of about 1.7 events per patient-year versus 5.7 with prandial and 3.0 with biphasic, and weight gain of 3.6 kg versus 6.4 kg and 5.7 kg. This trial is a major part of the rationale for starting with basal insulin in type 2 diabetes.
Safety
Hypoglycaemia is the dose-limiting adverse effect, though rates are lower than with isophane insulin. The dose-dependent and often sub-24-hour duration means that once-daily use can leave a gap in basal cover towards the end of the interval, and twice-daily dosing is frequently required. Detemir's lower molar potency means unit doses are typically higher than for other basal insulins; this is expected and does not indicate resistance, but it is a common source of confusion when switching, and unit-for-unit conversion between basal insulins is not appropriate. Weight gain is less than with other insulins but not absent. Hypokalaemia, injection-site lipohypertrophy from poor site rotation, and local injection reactions occur as with all insulins. Uncommon effects include systemic insulin allergy, lipoatrophy, peripheral oedema and transient refractive change on rapid glycaemic improvement. Renal or hepatic impairment reduces insulin clearance. Concurrent thiazolidinedione therapy increases fluid retention and heart-failure risk. Detemir must not be mixed with other insulins. Recurrent hypoglycaemia causes hypoglycaemia unawareness with implications for driving; UK drivers on insulin must comply with DVLA requirements. Anyone still using detemir where supply has ceased needs a planned, supervised transition to an alternative basal insulin rather than an ad hoc substitution. Non-medical use of any insulin by people without diabetes has caused deaths and permanent hypoglycaemic brain injury.
Regulatory status
| Jurisdiction | Status |
|---|---|
| United Kingdom | Licensed by the MHRA for the treatment of diabetes mellitus in adults, adolescents and children from 1 year of age; historically positioned in NICE guidance NG17 as a twice-daily basal insulin option for type 1 diabetes. Prescription-only medicine (POM). Availability has been affected by the manufacturer's global supply decisions, and prescribers should check current supply status. Included on the WHO Model List of Essential Medicines when long-acting analogues were added in 2021. |
| United States | FDA-approved in June 2005 for type 1 and type 2 diabetes. The manufacturer discontinued the product in the United States during 2024, citing global manufacturing constraints, formulary losses and the availability of alternatives; the pen presentation was withdrawn on 1 April 2024 and vials ceased to be available after 31 December 2024. It therefore has no current US market presence. |
| WADA (sport) | Prohibited at all times, in and out of competition, under section S4 of the WADA Prohibited List covering insulins and insulin-mimetics. Athletes with diabetes require a Therapeutic Use Exemption. |
Questions
The most widely accepted explanation is distributional. Because detemir circulates almost entirely bound to albumin, and albumin crosses the fenestrated liver endothelium more freely than the tight endothelium of muscle and fat, detemir may act relatively more on the liver and less on peripheral tissues, reducing lipogenesis. A central appetite-suppressing effect at the hypothalamus has also been proposed. Neither mechanism is proven, but the clinical observation itself is one of the most reproducible findings in the detemir literature.
Detemir has lower molar potency than human insulin, so the 100 units/mL product is formulated at four times the molar concentration: 2,400 nmol/mL against 600 nmol/mL for human insulin. The 'unit' is a biological potency unit, not a fixed mass, so higher unit numbers reflect the formulation rather than any resistance. It also means unit-for-unit switching between basal insulins is not appropriate.
The manufacturer discontinued it in the United States during 2024 (pens from April 2024 and vials after December 2024), citing manufacturing constraints, formulary losses and available alternatives, not any safety problem. Availability elsewhere has also been affected by the same global supply decisions. Anyone currently using it should discuss a planned transition with their diabetes team rather than assume continuity of supply.
Both are acylated at lysine B29 with the B30 threonine removed, but detemir carries a fourteen-carbon fatty mono-acid attached directly, while degludec carries a sixteen-carbon fatty diacid attached through a glutamyl spacer. That difference gives degludec far stronger albumin binding and the ability to form soluble multihexamer chains, producing a 25-hour half-life against detemir's 5 to 7 hours and a duration beyond 42 hours against detemir's 12 to 24.
Yes, frequently. Its duration is dose-dependent and at ordinary doses commonly falls short of 24 hours. In the 52-week head-to-head trial against glargine, roughly half of participants required twice-daily administration to reach target. This is the main practical trade-off against its weight advantage.