Japan Study Finds Insulin Degludec May Be Safer and More Cost-Effective Than Glargine U300 for Type 1 Diabetes

A study from Japan offers important new guidance for Americans living with Type 1 diabetes who rely on long-acting "basal" insulin — specifically comparing two modern options that many US patients currently use.

What the Researchers Did

Scientists at Osaka University's Graduate School of Pharmaceutical Sciences conducted a thorough systematic review and network meta-analysis, pooling data from nine randomized controlled trials. Their goal was to compare two widely prescribed long-acting insulins — insulin degludec U100 (Tresiba®) and insulin glargine U300 (Toujeo®) — in adults with Type 1 diabetes (T1D). Because no large head-to-head trial existed between these two insulins, the researchers used an indirect statistical comparison method to draw meaningful conclusions.

Why an International Perspective Matters

Japan's universal healthcare system and rigorous pharmaceutical research standards make it a trusted source for real-world drug comparisons. Japanese researchers often conduct cost-effectiveness analyses from a broader "societal" viewpoint — accounting for lost productivity, caregiver burden, and hospitalization — not just insurance costs. This approach can reveal savings that standard US drug comparisons often miss, making their findings especially relevant for American patients and policymakers.

Key Findings

Equal Blood Sugar Control

Both insulins performed equally well at lowering HbA1c (a 3-month blood sugar average) and fasting plasma glucose (FPG). In US-friendly units, the difference in fasting blood sugar was approximately 20 mg/dL (converted from –1.12 mmol/L), slightly favoring degludec — though this was borderline significant. Pre-breakfast blood sugar readings were also comparable between the two insulins.

Fewer Dangerous Low Blood Sugars With Degludec

This is where the findings become clinically striking. Degludec U100 was associated with:

• 56% lower risk of severe hypoglycemia (dangerously low blood sugar requiring outside help) compared to glargine U300 (HR 0.44)
• 81% lower risk of severe nocturnal hypoglycemia (dangerous nighttime lows) (HR 0.19)
• Lower total and basal insulin doses needed to achieve the same control

For context, the American Diabetes Association (ADA) identifies severe hypoglycemia as one of the most serious and potentially life-threatening complications of insulin therapy. Reducing that risk by more than half is clinically significant.

Cost Savings for US Patients

The cost-effectiveness analysis projected that US patients using degludec U100 instead of glargine U300 could gain an additional 0.0267 quality-adjusted life years (QALYs) — a measure of health benefit — while saving approximately $986 per patient per year. That makes degludec a "dominant" treatment option: better outcomes at lower cost.

Why This Matters for US Patients

Currently, both Tresiba® (degludec U100) and Toujeo® (glargine U300) are widely covered by US insurance plans and recommended within ADA guidelines as acceptable basal insulin options for Type 1 diabetes. However, this Japanese research suggests that if you are experiencing nighttime low blood sugars or frequent severe hypoglycemic episodes on glargine U300, switching to degludec U100 — in consultation with your endocrinologist — may meaningfully reduce that risk. The potential annual savings of nearly $1,000 per patient is also highly relevant given the ongoing US insulin affordability crisis. Speak with your diabetes care team about whether insulin degludec may be a better fit for your individual needs.

Note: The researchers acknowledged that this was low-certainty indirect evidence. A large, direct head-to-head clinical trial would strengthen these conclusions.

Original Study Citation

Martin, Zhou, & Takagi. "Safety, efficacy, and cost-effectiveness of insulin degludec U100 versus insulin glargine U300 in adults with type 1 diabetes: a systematic review and indirect treatment comparison." International Journal of Clinical Pharmacy (2022). PMID: 35476308. DOI: 10.1007/s11096-022-01410-x