Continuous glucose monitoring (CGM) — small sensors worn for one to two weeks at a time that measure interstitial glucose every few minutes — has moved from a diabetes-management tool to a broader metabolic-assessment tool with applications across longevity medicine and increasingly in psychiatry. The clinical utility is not in diabetes diagnosis (A1c and fasting glucose remain the standards there) but in surfacing patterns of glucose dysregulation that the standard tests miss, in personalizing dietary recommendations, and in revealing the metabolic-mood connections that affect daily psychiatric symptoms.
What CGM reveals that standard testing misses. Postprandial glucose excursions — the rises and falls after meals — vary enormously between individuals and are largely invisible to fasting glucose and A1c measurements. The patient who has "normal" fasting glucose but spikes to 180+ after every meal has substantial glucose dysregulation that fasting numbers do not capture. CGM also reveals overnight glucose patterns, dawn phenomenon variations, and the glucose response to specific foods that allows for genuinely personalized dietary recommendations rather than generic guidance.
The mood-metabolic connection becomes visible. Many patients with anxiety, irritability, fatigue, and concentration difficulties have glucose patterns that contribute to their symptoms. Postprandial spikes followed by reactive hypoglycemia produce anxiety, jitteriness, and concentration problems that mimic primary psychiatric symptoms. The patient who eats a high-carbohydrate breakfast and has anxiety at mid-morning may be experiencing reactive hypoglycemia. CGM makes this visible and actionable in a way that subjective symptom reporting alone does not.
The clinical applications in psychiatry are emerging. CGM is reasonable to consider in: patients with anxiety or irritability patterns that follow eating; patients with refractory mood disorders where metabolic contribution is suspected; patients undergoing dietary interventions (including ketogenic) where confirmation of metabolic state is useful; patients on antipsychotics with metabolic concerns where ongoing glucose monitoring informs medication management; patients in the acceleration window who are motivated to optimize their metabolic substrate. The cost has come down — direct-to-consumer CGM is increasingly accessible — but the interpretation requires clinical guidance.
The personalization opportunity is substantial. Research from the Weizmann Institute and others has shown that the glycemic response to identical foods varies enormously between individuals based on microbiome, genetics, metabolic state, and other factors. The patient who tolerates oats well may spike on bananas; the patient who handles rice may not handle potatoes; the standard generic dietary recommendations average across populations that are not uniform. CGM-guided dietary work allows for individualized recommendations grounded in the patient's own data — a step beyond the standard "Mediterranean diet" advice.
The clinical caveat is interpretation. CGM data without clinical guidance can produce anxiety, obsessive food relationships, and over-correction. The patient who watches their glucose curve in real time may develop hypervigilance that is itself a psychiatric concern. The intervention is therefore best paired with a clinician who can interpret patterns, guide dietary adjustments, and discontinue monitoring when the useful data has been extracted. CGM is a clinical tool, not a consumer device to be worn indefinitely without guidance.