Normal menstruation parameters

Parameter	Normal	Abnormal
Frequency	≥24 and ≤38 days	Absent (no bleeding): amenorrhea
		Frequent (<24 days)
		Infrequent (>38 days)
Duration	≤8 days	Prolonged (>8 days)
Regularity	Regular: shortest to longest cycle variation: ≤7 to 9 days*	Irregular: shortest to longest cycle variation: ≥10 days
Flow volume (patient determined)	Patient considers normal	Patient considers light
		Patient considers heavy
Intermenstrual bleeding (bleeding between cyclically regular onset of menses)	None	Random
		Cyclic (predictable): Early cycle Mid cycle Late cycle
Unscheduled bleeding on progestin±estrogen gonadal steroids (contraceptive pills, rings, patches, IUDs, or injections)	Not applicable for patients not on gonadal steroid medication	Present
	None (for patients on gonadal steroid medication)

IUDs: intrauterine contraceptive devices.

* Normal variation depends on age; these data are calculated excluding short and long outliers.

Data from:

Fraser IS, Critchley HO, Munro MG, Broder M. A process designed to lead to international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding. Fertil Steril 2007; 87:466.
Fraser IS, Critchley HO, Munro MG, Broder M. Can we achieve international agreement on terminologies and definitions used to describe abnormalities of menstrual bleeding? Hum Reprod 2007; 22:635.
Fraser IS, Munro MG, Broder M, Critchley HO. International recommendations on terminologies and definitions for normal and abnormal uterine bleeding. Semin Reprod Med 2011.

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