10-Day Water Fast - August-September 2025
Ketones and glucose data during the fast
Complete data from my 10-day water fast (Aug 25 - Sep 4, 2025) and 12 days of refeeding: daily weight, ketones, glucose, sleep, heart rate, and HRV. Part of my fasting results series - see all my fasts and cross-fast comparisons on the Results page. N=1 data, a reference point, not a prescription.
Weight (scale), Sleep and Readiness (Oura Ring)
These are my bloodwork results from the final hour of my 10-day water fast (Sep 4) on the left and another full panel after refeeding on the right (Oct 14)
Blood Results
Heart Health: 76 (pre-fast) -> 54 (fast) -> 92 (refeeding)
Fitness: 87 (pre-fast) -> 63 (fast) -> 85 (refeeding)
Metabolism: 78 (pre-fast) -> 65 (fast) -> 90 (refeeding)
Inflammation: 84 (pre-fast) -> 76 (fast) -> 95 (refeeding)
Sleep: 81 (pre-fast) -> 75 (fast) -> 84 (refeeding)
Hormone Balance: 90 (pre-fast) -> 81 (fast) -> 94 (refeeding)
Cognition: 87 (pre-fast) -> 78 (fast) -> 90 (refeeding)
Gut Health: 93 (pre-fast) -> 77 (fast) -> 94 (refeeding)
Endurance: 86 (pre-fast) -> 84 (fast) -> 86 (after refeeding)
Recovery: 94 (pre-fast) -> 90 (fast) -> 98 (refeeding)
Summary of All 10 Biomarker Categories: Pre-fast (Dec 2024) vs Fast (Sep 2025) vs Refeed (Oct 2025)
Biomarker Categories
Sleep: 81 (pre-fast) -> 75 (fast) -> 84 (refeed)
Fitness: 87 -> 63 -> 85
Endurance: 86 -> 84 -> 86
Cognition: 87 -> 78 -> 90
Metabolism: 78 -> 65 -> 90
Heart Health: 76 -> 54 -> 92
Gut Health: 93 -> 77 -> 94
Hormone Health: 90 -> 81 -> 94
Inflammation: 84 -> 76 -> 95
Recovery: 94 -> 90 -> 98
Total Testosterone
Total Testosterone
Feb 2010: 825 ng/dL (not on the graph)
Jan 2023: 1,036 ng/dL (not on the graph)
Jun 2023: 821 ng/dL (not on the graph)
Dec 2024: 969 ng/dL
Feb 2025, at the end of my previous 9-day fast: 131 ng/dL
May 2025: 564 ng/dL
Aug 2025, before this 10-day fast: 671 ng/dL
Sep 2025, at the end of last 10-day fast: 495 ng/dL
Oct 2025, after refeeding: 882 ng/dL
Electrolytes, at the end of the fast
My typical daily electrolyte intake during extended fasts - water with pink salt, Ultima electrolytes (2-3 packets) and a bottle of San Pellegrino mineral water