Table 3 .

Current and Piecewise Regression-Derived Reference Intervals (Lower Reference Limit 2.5th Percentile Value and Upper Reference Limit 97.5th Percentile Value) for Adults Aged 20-79 Years^a

Variable	Age, y	Current Reference Intervalsb	Age, y	Piecewise Regression-Derived Reference Intervals
RBC count, million cells/µL
Male	Adults	4.32-5.72	20-35 36-50 51-60 61-79	4.42-5.82 4.23-5.82 4.23-5.69 3.90-5.69
Female	Adults	3.90-5.03	20-79	3.72-5.20
Hemoglobin, g/dL
Male	Adults	13.5-17.5	20-35	13.5-17.5
			36-55	13.5-17.3
			56-79	12.4-17.3
Female	Adults	12.0-15.5	20-25	11.1-15.4
			26-30	11.1-15.2
			31-40 41-45 46-50 51-79	10.6-15.2 10.6-15.5 10.6-15.9 11.4-15.9
Hematocrit, %
Male	Adults	38.8-50.0	20-35 36-60 61-70	40.2-51.0 38.8-51.0 37.0-51.0
			71-79	35.0-51.0
Female	Adults	34.9-44.5	20-45 46-50	32.5-45.2 32.5-46.8
			51-79	34.2-46.8
Mean cell volume, fL
Male	Adults	81.2-95.1	20-50 51-79	81.2-97.3 81.2-100.0
Female	Adults	81.6-98.3	20-40 41-55 56-79	75.9-97.4 71.6-99.2 79.7-99.2
Mean cell hemoglobin, pgc
Male			20-35 36-50 51-75 76-79	27.1-33.4 27.1-34.0 27.1-34.5 24.8-34.5
Female			20-40 41-79	24.7-33.7 24.7-34.3
Mean cell hemoglobin concentration, g/dLc
Male			20-55 56-79	32.4-36.0 32.4-35.7
Female			20-60 61-79	32.1-35.8 32.1-35.6
Red cell distribution width, %
Male	Adults	11.8-15.6	20-45 46-50 51-70 71-79	11.3-13.8 11.5-13.8 11.5-14.8 11.7-14.8
Female	Adults	11.9-15.5	20-45 46-79	11.3-15.6 11.4-15.6

^aData from National Health and Nutrition Examination Survey 1999 to 2012 (supplemental data).

^bValues from Mayo Clinic.²¹

^cCurrent reference intervals are not provided by Mayo Clinic.²¹