At what age do girls typically start menstruating?

Age of Menarche in Girls

Girls typically begin menstruating at a median age of 12.43 years, with 90% of all US girls menstruating by age 13.75 years. 1

Normal Age Range for Menarche

• Less than 10% of US girls start menstruating before age 11 years 1
• The average age range for menarche is 12-13 years 2
• By age 13.75 years, 90% of all US girls have achieved menarche 1
• Girls initiate puberty on average between ages 8 and 10 years, with menarche occurring later in the pubertal sequence 3

Racial and Ethnic Variations

Menarche timing varies significantly by race and ethnicity, which is clinically important to recognize. 3

• Non-Hispanic Black girls experience menarche significantly earlier than non-Hispanic white girls at the 10%, 25%, and 50% percentiles 1
• Mexican American girls reach menarche significantly earlier than white girls only at the 25% percentile 1
• These racial differences should be considered when evaluating individual patients for delayed or precocious puberty 1

Expected Pubertal Progression

• By age 11 years, most girls have achieved Tanner stage 2 breast development 3
• Girls who have not achieved Tanner stage 2 breast development by age 13 years require evaluation for pubertal delay 4
• Failure to progress in pubertal stage for ≥12 months warrants clinical evaluation 4

When to Be Concerned

Early Menarche (Precocious Puberty)

• Menarche before age 8 years requires immediate evaluation for central or peripheral causes of precocious puberty 5
• Hormonal panel including FSH, LH, and estradiol should be obtained to differentiate between central and peripheral causes 5
• Pelvic ultrasound and referral to pediatric endocrinology are mandatory for all suspected cases 5

Delayed Menarche (Primary Amenorrhea)

• Primary amenorrhea is defined as absence of menarche by age 15 years, or by age 13 years in the absence of secondary sexual characteristics 6
• If no breast development by age 13 years, this represents delayed puberty requiring earlier intervention 6
• If breast development has occurred but no menarche by age 16 years, proceed with full evaluation 6

Clinical Implications

Early menarche (before age 12 years) is associated with increased cardiovascular risk factors in adulthood, including hypertension and metabolic abnormalities. 4 This underscores the importance of documenting menarche timing as part of long-term health risk assessment.