A new PPG-based method could allow smartwatches to monitor metabolic health without the need for blood tests
Garmin is intensifying its research into metabolic health with a newly published patent for non-invasive HbA1c estimation.
The USPTO filing—granted in early February—describes a system that uses the optical sensors on a Garmin watch to estimate glycated hemoglobin—a critical marker that reflects a user’s average blood sugar levels over several months.
Unlike current continuous glucose monitors (CGMs) that track real-time fluctuations, Garmin’s proposed method focuses on long-term metabolic trends, using light-based spectroscopy to analyze blood composition directly through the skin.
The technology relies on a multi-wavelength photoplethysmography (PPG) array. By emitting specific wavelengths of light, the sensors can distinguish among oxygenated, deoxygenated, and glycated hemoglobin based on how the light is absorbed and reflected.
The system then processes these ‘AC-to-DC’ signal ratios through advanced algorithms to calculate an HbA1c percentage.
The patent also suggests this sensor array could simultaneously calculate both fractional and functional blood oxygen saturation, offering a much deeper window into blood chemistry than standard SpO2 sensors.
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An increased focus on serious health features
After a similar patent filed by the company appeared last summer, there appears to be a considered shift towards medical-grade diagnostics.
While the brand has historically focused on elite athletic metrics, a non-invasive HbA1c tool would appeal to a much broader audience, including those managing pre-diabetes or metabolic syndrome.
Plus, by focusing on HbA1c rather than real-time glucose—which is notoriously difficult to measure accurately via the skin—Garmin may have found a more viable optical path to metabolic tracking.
While a patent doesn’t guarantee an immediate feature, it confirms that Garmin is building a hardware foundation that could eventually enable the Fenix or Venu series to serve as a proactive metabolic health tracker.
