It is the opposite of hypermenorrhea which is more properly called menorrhagia.

A blood loss of greater than 80 ml or lasting longer than 7 days constitutes menorrhagia (also called hypermenorrhea).

Exceptionally heavy bleeding during periods is termed menorrhagia or hypermenorrhea, while light bleeding is called hypomenorrhea.

Some authors use menorrhagia exclusively when describing excessive quantity and hypermenorrhea for prolonged duration (although most use both terms interchangeably in the clinical setting).

High levels of masculinizing hormones: The most common signs are acne and hirsutism (male pattern of hair growth), but it may produce hypermenorrhea (very frequent menstrual periods) or other symptoms.