Non-Invasive Saliva Test May Detect Early Signs of Diabetes and Obesity: Study Finds - Video

A new study published in Applied Physiology, Nutrition, and Metabolism has found that insulin levels in saliva can be used as a non-invasive method to detect early signs of metabolic health issues, including Type 2 diabetes, obesity, and heart disease.

Hyperinsulinemia, or elevated insulin levels in the blood, is a well-established marker of poor metabolic health and a predictor of chronic diseases. While blood testing has been the standard, researchers now say that saliva testing could serve as a practical and less invasive alternative.

The study involved 94 healthy participants with a range of body sizes. After fasting, each participant consumed a standardized meal-replacement shake, provided saliva samples at multiple time points, and completed a finger-prick blood glucose test. Researchers found that individuals living with obesity had significantly higher saliva insulin levels compared to leaner participants, even though their blood glucose levels remained similar.

Dr. Hossein Rafiei, co-author of the study, highlighted another compelling finding: some lean participants also showed large spikes in saliva insulin after the meal. “The finding that some lean people have high insulin is intriguing. This indicates that saliva insulin may be more useful than measuring someone’s weight or waist size.”

The study also found that waist circumference had the strongest correlation with elevated saliva insulin, more so than BMI, age, or sex. “Our results also suggest that saliva insulin may be better than blood glucose at distinguishing between those who are more metabolically healthy and those who are more likely to live with hyperinsulinemia,” adds Dr. Rafiei.

Researchers hope this method could eventually lead to accessible screening tools that enable early interventions—well before chronic conditions take hold.

Reference: Hossein Rafiei and Jonathan Peter Little. 2025. Saliva insulin concentration following ingestion of a standardized mixed meal tolerance test: influence of obesity status. Applied Physiology, Nutrition, and Metabolism. 50: 1-8. https://doi.org/10.1139/apnm-2024-0532