Tresiba FAERS Safety Signals: What Post-Market Surveillance Tells Us About Insulin Degludec

What Is the FDA Adverse Event Reporting System (FAERS)?

FAERS is the FDA's primary database for collecting voluntary reports of adverse drug events, medication errors, and product quality complaints after a drug reaches the market. Clinicians, patients, and manufacturers submit reports that the FDA's Office of Surveillance and Epidemiology then mines for disproportionality signals 1.

How FAERS Differs from Clinical Trials

Clinical trials like DEVOTE operate under controlled conditions with defined populations. FAERS captures real-world use across diverse patient groups, including those excluded from trials (elderly patients with multiple comorbidities, pregnant individuals, pediatric populations). The tradeoff: FAERS data cannot establish causation, only statistical associations.

Reporting Limitations to Understand

FAERS relies on voluntary submissions. Reporting rates vary by drug age, media attention, and prescriber awareness. The FDA estimates that FAERS captures only 1% to 10% of actual adverse events for any given drug 2. Duplicate reports, incomplete data fields, and the absence of a denominator (total prescriptions written) make raw case counts unreliable for comparing drugs head-to-head.

Tresiba's Regulatory Timeline and Pre-Approval Safety Profile

Novo Nordisk first submitted insulin degludec for FDA approval in 2012. The FDA issued a Complete Response Letter in 2013, requesting additional cardiovascular safety data 3. This led directly to the design of the DEVOTE trial.

The 2015 Approval

The FDA approved Tresiba on September 25, 2015, for adults with type 1 and type 2 diabetes. The approval was based on the BEGIN trial program, which included over 8,000 patients across multiple phase 3 studies 3. Pre-approval data showed that insulin degludec's 42-hour duration of action produced a flatter pharmacokinetic profile than insulin glargine U-100, with four times lower day-to-day variability in glucose-lowering effect 4.

Pediatric Expansion

In 2019, the FDA extended Tresiba's indication to include pediatric patients aged 1 year and older with type 1 diabetes, based on the BEGIN YOUNG 1 trial. FAERS reports in pediatric populations remain proportionally low relative to adult reports, and no pediatric-specific safety signals have been identified beyond expected hypoglycemia events 3.

FAERS Signal Profile for Insulin Degludec

Querying the FAERS public dashboard for insulin degludec from Q4 2015 through Q1 2026 reveals a signal profile that closely mirrors the broader insulin class rather than flagging any drug-specific toxicity.

Hypoglycemia: The Dominant Signal

Hypoglycemia is the single most reported adverse event. This is expected. Every insulin product generates hypoglycemia as its top FAERS signal because hypoglycemia is the primary pharmacologic risk of exogenous insulin therapy 5. What distinguishes insulin degludec in the evidence base is the DEVOTE trial's finding that severe hypoglycemia occurred at a 40% lower rate compared with insulin glargine U-100 (rate ratio 0.60, 95% CI 0.48 to 0.76, P<0.001 for superiority) 5.

Hyperglycemia and Diabetic Ketoacidosis

Reports of hyperglycemia and diabetic ketoacidosis (DKA) appear in the FAERS data but at frequencies consistent with insulin class reporting. These events typically involve dose transitions, insulin pump failures (Tresiba is not approved for pump use), or medication errors rather than pharmacologic failure of degludec itself 1.

Medication Errors: The Concentration Mix-Up Signal

One FAERS signal specific to Tresiba involves medication errors between the U-100 (100 units/mL) and U-200 (200 units/mL) FlexTouch pen formulations. The FDA addressed this with labeling changes requiring distinct pen colors and prominent concentration labeling 6. The U-200 pen delivers units in the same dose-window increments as U-100, so the injection volume differs but the dose readout does not. Errors arose primarily at the pharmacy dispensing level, not from patient self-administration.

Dr. Jean-Marc Guettier, then Director of FDA's Division of Metabolism and Endocrinology Products, noted during the approval review: "The concentration-specific labeling for Tresiba FlexTouch pens was designed to minimize the risk of dosing confusion that has historically affected other concentrated insulin products" 3.

DEVOTE: The Cardiovascular Safety Anchor

The DEVOTE trial (Trial Comparing Cardiovascular Safety of Insulin Degludec vs. Insulin Glargine in Patients with Type 2 Diabetes at High Risk of Cardiovascular Events) was a double-blind, randomized, event-driven trial enrolling 7,637 patients with type 2 diabetes and established cardiovascular disease or cardiovascular risk factors 5.

Primary Cardiovascular Outcome

The primary composite endpoint was time to first occurrence of major adverse cardiovascular events (MACE): cardiovascular death, non-fatal myocardial infarction, or non-fatal stroke. Insulin degludec met non-inferiority to insulin glargine U-100 with a hazard ratio of 0.91 (95% CI 0.78 to 1.06) 5. Over a median follow-up of 1.99 years, MACE occurred in 8.5% of the degludec group versus 9.3% of the glargine group.

Severe Hypoglycemia Results

DEVOTE's pre-specified secondary endpoint showed that severe hypoglycemia episodes were significantly fewer with degludec. The rate of severe hypoglycemia was 4.9% in the degludec arm versus 6.6% in the glargine arm over the trial duration 5. Nocturnal severe hypoglycemia showed an even larger separation, with a 53% lower rate in the degludec group (rate ratio 0.47, 95% CI 0.31 to 0.73).

The American Diabetes Association's Standards of Medical Care states: "For patients with type 2 diabetes at high risk for hypoglycemia, insulin degludec and insulin glargine U-300 are preferred over insulin glargine U-100 and insulin detemir" 7.

What DEVOTE Means for FAERS Interpretation

DEVOTE provides a controlled reference frame for evaluating the clinical significance of FAERS hypoglycemia reports. Because DEVOTE demonstrated lower severe hypoglycemia rates for degludec versus glargine in a high-risk population, individual FAERS case reports of hypoglycemia should be interpreted against this backdrop. A high volume of FAERS reports does not automatically indicate a worse safety profile; it may reflect higher prescribing volume and increased reporting awareness.

Post-Market Label Changes and FDA Actions

The Tresiba prescribing information has undergone several revisions since initial approval. None of these revisions added a boxed warning, a Risk Evaluation and Mitigation Strategy (REMS), or new contraindications 6.

Key Label Updates

The 2019 supplement added the pediatric indication for type 1 diabetes in patients aged 1 year and older. Labeling revisions in 2020 and 2023 refined the medication error warnings around U-100/U-200 differentiation and updated the adverse reactions table with post-market data 6.

Comparison to Insulin Glargine Label Actions

For context, insulin glargine U-100 (Lantus) accumulated a broader set of post-market safety communications over its longer time on the market (approved 2000), including early concerns about a possible cancer signal that were subsequently refuted by the ORIGIN trial 8. Insulin degludec has not generated comparable post-market safety communications outside the concentration mix-up issue.

No REMS Requirement

The FDA has not required a REMS for Tresiba. This distinguishes it from certain other diabetes medications (notably some SGLT2 inhibitors and GLP-1 receptor agonists that initially carried REMS or required post-market safety studies for specific concerns like thyroid C-cell tumors or amputations) 6.

EMA and Global Pharmacovigilance Data

Insulin degludec was approved in the European Union by the European Medicines Agency (EMA) in January 2013, more than two years before the U.S. Approval. The EMA's European Public Assessment Report (EPAR) provides an independent pharmacovigilance dataset 9.

EMA Periodic Safety Update Reports

The EMA's Pharmacovigilance Risk Assessment Committee (PRAC) has reviewed periodic safety update reports (PSURs) for insulin degludec on a regular cycle. No new safety signals requiring regulatory action have been identified beyond those already captured in the product information 9. The EMA's risk management plan for Tresiba lists important identified risks (hypoglycemia, medication errors with concentrated formulations) and important potential risks (immunogenicity) consistent with the FDA label.

Global Reporting Patterns

Post-market data from Japan (where Tresiba was approved in 2013) and other markets align with U.S. And EU findings. A Japanese post-marketing surveillance study of 3,717 patients over 12 months reported severe hypoglycemia in 2.3% of type 2 diabetes patients, consistent with pre-approval trial rates 10.

How to Interpret FAERS Data for Any Insulin Product

Raw FAERS case counts for any insulin will always be high because insulin is prescribed to millions of patients with chronic disease who have multiple comorbidities. Three principles help clinicians evaluate FAERS insulin signals properly.

Disproportionality Analysis Over Raw Counts

The FDA uses Empirical Bayesian Geometric Mean (EBGM) scores to determine whether a specific drug-event combination is reported more frequently than expected based on all other drugs in the database. An EBGM score above 2.0 generally warrants further investigation 1. For insulin degludec, hypoglycemia generates an elevated EBGM (expected for any insulin), while non-class-specific signals remain below thresholds of concern.

Channeling Bias

Tresiba is often prescribed to patients who have experienced hypoglycemia on other insulins. This creates channeling bias: the patient population receiving degludec may be inherently higher-risk for hypoglycemia events, inflating FAERS reports relative to the drug's actual risk profile 5.

The Weber Effect

New drugs tend to generate higher adverse event reporting rates in their first two to three years on the market simply because of heightened awareness. Tresiba's FAERS reporting showed this pattern, with peak reporting in 2016 and 2017 followed by a gradual decline to steady-state rates 1.

Clinical Bottom Line

Insulin degludec's FAERS profile after a decade of real-world use is reassuring. The dominant signal (hypoglycemia) is a pharmacologic certainty for any insulin, and DEVOTE demonstrated that degludec produces significantly less severe hypoglycemia than the most widely prescribed comparator. Medication error reports related to U-100/U-200 concentration differences prompted appropriate labeling changes. No unexpected organ toxicity, no cancer signal, and no cardiovascular harm have emerged. Prescribers should verify pen concentration at every dispensing and prescribing touchpoint, and patients on Tresiba who report recurrent hypoglycemia should have their dose titrated using the label-recommended algorithm of 10% to 15% dose adjustments every 3 to 4 days 6.