The primary purpose of this study is to characterize the performance and utility of a novel breath acetone meter developed by Readout, Inc.

Inclusion Criteria:

• Ketogenic diet cohort: currently following a ketogenic or low-carbohydrate diet defined as less than 30 grams per day (ketogenic) or less than 100 grams per day (low-carbohydrate) as estimated by the individual. Subjects must have been following the diet before the beginning of the study period and must continue with the diet throughout the duration of the trial.
• High-carbohydrate diet cohort: currently following a diet that does not restrict dietary carbohydrate. Carbohydrate consumption should be greater than 100 grams per day as estimated by the individual. Subjects must have been following the diet before the study period and must continue with the diet throughout the duration of the trial.

Exclusion Criteria:

• Type-1 diabetes
• Insulin-dependent type-2 diabetes
• History of diabetic ketoacidosis
• Currently taking Warfarin or other blood thinners
• Currently taking a sodium-glucose cotransporter-2 (SGLT2) inhibitor
• Currently taking Disulfiram
• Unwilling to maintain their diet during the study period
• Unwilling to test blood and breath ketones five times per day
• Non-English speaking
• Persons who are unable or unwilling to follow the study protocol or who, for any reason, the research team considers not an appropriate candidate for this study, including non-compliance with screening appointments or study visits.

Individuals who are interested in the ketogenic diet or in tracking their ketones.