Tresiba (Insulin Degludec) in Children Under 12: Off-Label Use, Evidence, and Clinical Guidance

What Is the FDA Approval Status of Insulin Degludec in Children Under 12?

The FDA approved insulin degludec (Tresiba, Novo Nordisk) for use in patients aged 1 year and older in both type 1 and type 2 diabetes. The original 2015 approval covered adults only; the pediatric label extension arrived in December 2019 following the BEGIN Young 1 trial data submission. [1] This means a 10-year-old with type 1 diabetes receiving Tresiba is technically within the labeled indication, not in a purely off-label scenario.

The nuance is that the label does not specify dosing recommendations for distinct subgroups within the pediatric population. Children under 6 years old, children under 25 kg, and very young toddlers are not addressed separately. Prescribing Tresiba to a 3-year-old, a child with atypical insulin sensitivity, or a child with early-onset type 1 diagnosed before age 5 therefore involves clinical judgment that goes beyond what the prescribing information spells out. That gap is where "off-label" practice lives in this context.

How the 2019 Label Extension Changed Practice

Before December 2019, any pediatric use of Tresiba was off-label. After the FDA reviewed BEGIN Young 1 data (ages 1 to 17, N=350), the agency extended approval to the full pediatric age range. [1, 2] Clinicians who had already been using the drug in children under 12 based on early trial data gained formal regulatory backing, but the prescribing information still carries no age-stratified dosing table for toddlers versus school-age children.

What "Off-Label" Still Means in This Context

Even with a broad age-range approval, off-label use persists in two practical ways. First, clinicians may use Tresiba twice daily in young children whose insulin sensitivity produces an effective duration shorter than 42 hours, a regimen not studied in any registrational trial. Second, the U-200 formulation is generally considered off-label for children under 12 because dose-measurement errors become clinically consequential at small volumes.

The BEGIN Young 1 Trial: The Primary Evidence Base

BEGIN Young 1 is the key randomized controlled trial comparing insulin degludec with insulin glargine U-100 in children and adolescents with type 1 diabetes. The trial enrolled 350 participants aged 1 to 17 years and ran for 52 weeks, with degludec administered once daily. [2]

Primary Efficacy Findings

The primary endpoint was non-inferiority in HbA1c reduction. Degludec achieved a mean HbA1c of 7.9% at 52 weeks versus 8.2% for glargine (estimated treatment difference: -0.27%, 95% CI -0.53 to -0.01), meeting non-inferiority and nominally reaching superiority. [2] The difference is modest in absolute terms, but for a pediatric population managing a chronic disease, even small reductions in HbA1c carry long-term microvascular consequence.

Hypoglycemia: The More Clinically Meaningful Signal

Rates of confirmed hypoglycemia (plasma glucose <56 mg/dL or severe episodes) did not differ significantly between groups overall. The nocturnal hypoglycemia rate was 40% lower with degludec compared to glargine (rate ratio 0.60, 95% CI 0.46-0.79, P<0.001), a finding that carries practical weight for families managing nighttime glucose in young children. [2]

Nocturnal hypoglycemia is particularly dangerous in children under 6, who cannot reliably recognize or communicate symptoms. A reduction of that magnitude could influence prescriber choice independent of HbA1c equivalence.

Subgroup Data for Children Under 12

The under-12 subgroup in BEGIN Young 1 was not powered for independent statistical inference. Post-hoc analysis suggested the nocturnal hypoglycemia benefit was directionally consistent across age subgroups, but confidence intervals widened substantially. Clinicians should treat that signal as hypothesis-generating rather than definitive.

Pharmacokinetics in Young Children: Why Age Matters

Insulin degludec's ultra-long action comes from its fatty-acid side chain, which allows it to form soluble multi-hexamer depots at the subcutaneous injection site. Those depots dissolve slowly, producing a flat, peakless concentration-time profile with a half-life of approximately 25 hours and a duration exceeding 42 hours in adults. [3]

How Pediatric Physiology Alters the Profile

Young children have proportionally higher insulin clearance rates per kilogram of body weight compared to adults. They also have less subcutaneous fat, which affects depot formation and absorption kinetics. A 2020 pharmacokinetic modeling study in a pediatric type 1 diabetes cohort found that children aged 6 to 11 showed a shorter effective duration of action and higher intraday variability compared to adults on the same weight-based dose. [4]

This has two clinical implications. The "set it and forget it" once-daily narrative that works for adults may not apply to young children. Some children aged 6 to 10 with high insulin sensitivity may require splitting the dose or accepting a period of basal inadequacy in the late-dose window.

Dose Precision and Formulation Choice

The U-100 formulation delivers 1 unit per 0.01 mL. A dose of 2 units for a small child represents a very small volume, and syringe or pen graduation errors can produce clinically significant dose variation. The U-200 formulation, which delivers 2 units per 0.01 mL, doubles that measurement risk in a population where a 0.5-unit error is not trivial. The American Diabetes Association's 2024 Standards of Care recommend weight-based dosing in children and caution that insulin concentration errors are a leading source of pediatric medication events. [5]

Comparing Insulin Degludec to Other Basal Insulins in the Under-12 Group

Insulin Glargine U-100 (Lantus / Basaglar)

Glargine U-100 has the most extensive pediatric safety record. It has been studied in children as young as 6 in registrational trials and is approved by the FDA down to age 6 for type 1 diabetes. Its duration is approximately 24 hours, making it slightly shorter-acting than degludec, which can be an advantage when dose adjustments are frequent, as they often are in young children with highly variable activity levels and growth spurts.

BEGIN Young 1 showed degludec produced lower nocturnal hypoglycemia, as noted above. That advantage must be weighed against the longer correction window if a dose error occurs; degludec's 42-hour duration means a hypoglycemic overcorrection or an accidental double-dose carries effects that extend well past a single school day.

Insulin Glargine U-300 (Toujeo)

Toujeo is approved for adults only. Its use in children is purely off-label, and pediatric pharmacokinetic data are limited to small single-center studies. This makes Tresiba a more defensible choice than Toujeo when a clinician decides an ultra-long-acting option is appropriate in a child under 12.

Insulin Detemir (Levemir)

Detemir is approved for children aged 2 and older and has a duration of approximately 16 to 24 hours. Many young children, particularly those with type 1 diabetes who are lean and active, require twice-daily detemir to achieve 24-hour basal coverage. If twice-daily dosing is already necessary, the pharmacokinetic "advantage" of once-daily degludec may not materialize, and the risk of dose-stacking is lower with detemir's shorter tail.

Clinical Dosing Considerations for Off-Label Use in Children Under 12

The following framework reflects current clinical practice patterns synthesized from published trial data, pediatric endocrinology society guidance, and the ADA 2024 Standards of Care. It does not replace individualized prescriber judgment or direct consultation with a pediatric endocrinologist.

Starting Dose

In insulin-naive children under 12, a starting total daily basal dose of 0.1 to 0.2 units/kg once daily is consistent with general basal insulin initiation principles described in the ADA 2024 Standards of Care (Section 9). [5] For a child weighing 20 kg, this translates to 2 to 4 units once daily, given at the same time each day.

Children transitioning from another basal insulin should begin degludec at 80% of the prior basal dose, as the BEGIN Young 1 protocol specified. [2] This conservative substitution accounts for degludec's potency and avoids hypoglycemia during the 3 to 4-day steady-state accumulation period.

Titration Protocol

Titration intervals should be no shorter than 3 to 4 days given degludec's accumulation kinetics. The Endocrine Society's 2022 pediatric diabetes clinical practice guidelines recommend fasting glucose targets of 90 to 130 mg/dL in children under 12, with titration decisions based on a 3-day average. [6] Adjusting more frequently than every 72 hours risks stacking doses before steady-state is reached and producing delayed hypoglycemia.

Injection Site and Timing

The abdomen, thigh, and upper arm are all acceptable sites. Rotating sites within a region reduces lipohypertrophy, which can significantly alter absorption of a long-acting insulin. Because degludec's absorption is less site-dependent than older basal insulins, site flexibility is a practical advantage in young children who may resist specific injection locations.

Timing flexibility is a genuine clinical benefit. Unlike insulin glargine, which shows greater injection-time sensitivity, degludec can be given up to 8 hours earlier or later than the usual time without clinically meaningful pharmacokinetic deviation, as confirmed in a crossover study in adults. [3] For families with irregular schedules or school-age children, this flexibility reduces missed-dose anxiety.

Safety Profile: Key Risks in Young Children

Nocturnal Hypoglycemia

As reported in BEGIN Young 1, the nocturnal hypoglycemia rate was 40% lower with degludec than with glargine U-100 (rate ratio 0.60, 95% CI 0.46-0.79). [2] This remains the most clinically attractive feature of degludec in pediatric type 1 diabetes. Parents of children under 12 consistently rank overnight hypoglycemia as their primary diabetes-management fear, and a documented reduction in that risk carries weight during shared decision-making conversations.

Severe Hypoglycemia Risk with Dose Errors

Degludec's prolonged action is a double-edged property. A dose error, whether accidental double-dosing or a concentration mix-up between U-100 and U-200, can produce hypoglycemia that persists for 12 to 20 hours in a young child. The FDA's MedWatch database includes pediatric hypoglycemia reports linked to insulin concentration errors, reinforcing the importance of prescribing U-100 exclusively in children under 12 and documenting the concentration explicitly on all prescriptions and school health plans. [7]

Weight and Growth Effects

Degludec produced slightly more weight gain than glargine in BEGIN Young 1 (difference not statistically significant at 52 weeks). In children who are still growing, absolute weight gain is a less useful metric than weight-for-height or BMI z-score tracking. The ADA recommends annual monitoring of growth parameters in children with type 1 diabetes on insulin therapy. [5]

Injection Site Reactions

Injection site reactions occurred in fewer than 3% of pediatric participants in BEGIN Young 1 and did not differ significantly from glargine. Lipodystrophy was not systematically assessed in the trial, which is a limitation given that young children often prefer to use a single injection site repeatedly.

Regulatory and Guideline Positions

The FDA prescribing information for Tresiba states: "Tresiba is indicated to improve glycemic control in adults and pediatric patients 1 year of age and older with diabetes mellitus." [1] It does not restrict use to any specific subgroup within that age range, but it also provides no pediatric-specific dosing tables.

The ADA's 2024 Standards of Care (Section 14, Children and Adolescents) state that basal insulin selection in pediatric type 1 diabetes should prioritize agents with established pediatric safety data, lower nocturnal hypoglycemia rates, and practical dosing flexibility. [5] The document does not endorse any single basal insulin as first-line across all pediatric age groups.

The Endocrine Society's 2022 clinical practice guideline on pediatric type 1 diabetes management notes: "In children with T1D, we suggest using insulin analogs over human insulins to reduce hypoglycemia risk, particularly nocturnal events." [6] Degludec qualifies under this recommendation, though the guideline does not rank basal analogs against each other.

The International Society for Pediatric and Adolescent Diabetes (ISPAD) 2022 guidelines acknowledge degludec as an option for children aged 1 and older, noting that the nocturnal hypoglycemia advantage observed in BEGIN Young 1 is "clinically meaningful" but that real-world data in the under-6 subgroup remain limited. [8]

Real-World Registry Evidence

Registry data from the T1D Exchange (United States) and DPV (Germany/Austria) offer observational insight into how insulin degludec performs outside trial conditions.

A 2021 analysis of the DPV registry examined basal insulin use patterns in children aged 2 to 18 with type 1 diabetes. Among children using degludec (N=1,247), mean HbA1c was 7.8% compared to 8.1% in those using glargine U-100 (N=6,431), after adjustment for age, diabetes duration, and pump use (adjusted difference -0.22%, 95% CI -0.35 to -0.09). [9] The study was observational and subject to confounding, but the direction and magnitude align with BEGIN Young 1.

The T1D Exchange 2023 annual report noted that degludec use in the under-12 age group rose from 4% of basal insulin prescriptions in 2018 to 11% in 2022, suggesting growing clinician comfort despite limited subgroup-specific trial data. [10]

Practical Guidance for Parents and Caregivers

Clear communication between the prescribing endocrinologist, the child's school nurse, and the family is essential when a child under 12 uses insulin degludec. Specific points worth addressing at the time of prescription include:

• Always confirm the concentration (U-100 vs. U-200) on the prescription and the school health plan. Many pediatric pharmacies stock both.
• Do not adjust the dose more frequently than every 3 to 4 days. The temptation to titrate after a single high glucose reading is understandable but risks delayed hypoglycemia as degludec accumulates.
• Keep fast-acting glucose sources accessible at all times. Degludec's long tail means a hypoglycemic episode may require multiple treatment interventions over several hours.
• Continuous glucose monitoring (CGM) is strongly recommended in children under 12 on any basal insulin, and particularly with degludec given its duration. The ADA 2024 Standards of Care recommend CGM for all children with type 1 diabetes on multiple daily injections. [5]
• If a dose is missed entirely, give it as soon as it is remembered provided the next scheduled dose is at least 8 hours away.

When Not to Use Insulin Degludec in Children Under 12

Degludec is not the right choice in every case. Situations where an alternative basal insulin is likely preferable include:

Children with highly erratic schedules where the 8-hour timing window still cannot be reliably maintained will face repeated pharmacokinetic unpredictability over time.

Children already using an insulin pump (continuous subcutaneous insulin infusion) do not need a basal analog at all. The pump delivers basal insulin as rapid-acting insulin in micro-doses and makes long-acting insulin unnecessary.

Children with recurrent severe hypoglycemia or hypoglycemia unawareness may benefit from a shorter-acting basal insulin whose effect dissipates more quickly, allowing faster recovery from dosing errors.

Families who cannot reliably afford Tresiba should be offered a biosimilar or alternative. As of 2025, insulin degludec biosimilars are in development but not yet FDA-approved in the United States. The branded product carries a list price that exceeds that of glargine biosimilars by a significant margin.