Endurance Biomarkers
Tracking my endurance biomarkers across 2.5 years of fasting – including results from my 7-, 9-, and 10-day water fasts.
The end of the 10-day fast - Sep 4, 2025
After 40 days of refeeding - Oct 14, 2025
Ferritin
Ferritin, ng/dL
Jan 27, 2023 - 74
Jun 30, 2023 - 76
Dec 17, 2024 - 85
Feb 11, 2025 (9-day fast) - 158
Sep 4, 2025 (10-day fast) - 183
Oct 14, 2025 - 58
Hemoglobin
Hemoglobin, g/dL
Jan 27, 2023 - 14.5
Jun 30, 2023 - 14.1
Dec 17, 2024 - 14.6
Feb 11, 2025 (9-day fast) - 14.3
Sep 4, 2025 (10-day fast) - 15
Oct 14, 2025 - 14.9
Platelets
Platelets, thousands/uL
Jan 27, 2023 - 298
Jun 30, 2023 - 288
Dec 17, 2024 - 290
Feb 11, 2025 (9-day fast) - 273
Sep 4, 2025 (10-day fast) - 255
Oct 14, 2025 - 282
Transferrin Saturation
Transferrin Saturation, %
Jan 27, 2023 - 35
Jun 30, 2023 - 29
Dec 17, 2024 - 69
Feb 11, 2025 (9-day fast) - 11
Sep 4, 2025 (10-day fast) - 38
Oct 14, 2025 - 48
Vitamin B12
Vitamin B12, pg/mL
Jan 27, 2023 - 580
Jun 30, 2023 - 472
Dec 17, 2024 - 520
Feb 11, 2025 (9-day fast) - 1,548
May 27, 2025 - 529
Sep 4, 2025 (10-day fast) - 1,605
Oct 14, 2025 - 400
Iron
Iron, ug/dL
Jan 27, 2023 - 95
Jun 30, 2023 - 72
Dec 17, 2024 - 176
Feb 11, 2025 (9-day fast) - 74
Sep 4, 2025 (10-day fast) - 86
Oct 14, 2025 - 128
Hematocrit
Hematocrit, %
Jan 27, 2023 - 43.7
Jun 30, 2023 - 43.2
Dec 17, 2024 - 45.3
Feb 11, 2025 (9-day fast) - 42.4
Sep 4, 2025 (10-day fast) - 44.9
Oct 14, 2025 - 46.0
MPV
MPV, fL
Jan 27, 2023 - 10.6
Jun 30, 2023 - 10.0
Dec 17, 2024 - 10.1
Feb 11, 2025 (9-day fast) - 10.0
Sep 4, 2025 (10-day fast) - 9.9
Oct 14, 2025 - 10.3
TIBC
TIBC, ug/dL
Jan 27, 2023 - 274
Jun 30, 2023 - 246
Dec 17, 2024 - 254
Feb 11, 2025 (9-day fast) - 223
Sep 4, 2025 (10-day fast) - 224
Oct 14, 2025 - 267
MCH
MCH, pg
Jan 27, 2023 - 32
Jun 30, 2023 - 31.2
Dec 17, 2024 - 31.7
Feb 11, 2025 (9-day fast) - 32.2
Sep 4, 2025 (10-day fast) - 32.4
Oct 14, 2025 - 32.0
MCHC
MCHC, g/dL
Jan 27, 2023 - 33
Jun 30, 2023 - 33
Dec 17, 2024 - 32
Feb 11, 2025 (9-day fast) - 34
Sep 4, 2025 (10-day fast) - 33
Oct 14, 2025 - 32
MCV
MCV, fL
Jan 27, 2023 - 96.5
Jun 30, 2023 - 95.6
Dec 17, 2024 - 98.5
Feb 11, 2025 (9-day fast) - 95.5
Sep 4, 2025 (10-day fast) - 97.0
Oct 14, 2025 - 98.7
RBC
RBC, x10E6/µL
Jan 27, 2023 - 4.5
Jun 30, 2023 - 4.5
Dec 17, 2024 - 4.6
Feb 11, 2025 (9-day fast) - 4.4
Sep 4, 2025 (10-day fast) - 4.6
Oct 14, 2025 - 4.7
RDW
RDW, %
Jan 27, 2023 - 12.2
Jun 30, 2023 - 12.0
Dec 17, 2024 - 12.2
Feb 11, 2025 (9-day fast) - 11.7
Sep 4, 2025 (10-day fast) - 12.4
Oct 14, 2025 - 13.3