Missed, delayed, or inconsistent periods or menstrual bleeding patterns that are out of the ordinary.

See a doctor right away if:

• You suddenly get a fever and feel sick after using tampons.

See a doctor if:

• Your periods suddenly stop for more than 90 days, and you're not pregnant.
• Your periods become irregular after having been regular.
• You bleed for more than seven days.
• You bleed more heavily than usual or soak through more than one pad or tampon every hour or two.
• Your periods are less than 21 days or more than 35 days apart.
• You bleed between periods.
• You develop severe pain during a period.