How many days late is considered a late period?

Reviewed by Yoshinori Abe, MD

Internal Medicine

A period is generally considered late when it hasn't started within 7 days of its expected date, based on your usual cycle. Most menstrual cycles last between 21 and 35 days, so tracking your cycle helps identify what's normal for you. A missed or late period can be caused by many factors, including stress, hormonal changes, weight fluctuations, medications, pregnancy, or underlying health conditions like thyroid disorders or polycystic ovary syndrome (PCOS).

If your period is late and you're unsure why, understanding the potential cause is the first step toward peace of mind. Take a free, instant, online symptom check to explore possible reasons based on your unique situation and get clear guidance on what to do next.

Reviewed for medical accuracy: 07/15/2026

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Explanation

Most women have cycles that last between 21 and 35 days. That means if you normally have a 28-day cycle and your period hasn't started by day 35, it would be defined as late.

Small changes of a few days in your cycle from month to month can be normal and is not necessarily a sign of a more serious problem.

Many things can change your cycle including stress, exercise habits, or changes in your weight and overall health. If your period is typically regular and is delayed by a full week or more, it could be a good idea to keep a diary of your cycle and use Ubie's free AI-powered symptom checker to help identify possible causes before talking with a doctor.

(References)

deProsse CA, Keettel WC. The missed menstrual period. Postgrad Med. 1977 Jan;61(1):251-2, 254, 256. doi: 10.1080/00325481.1977.11714526. PMID: 189296.
Thiyagarajan DK, Basit H, Jeanmonod R. Physiology, Menstrual Cycle. 2024 Sep 27. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan–. PMID: 29763196.
Nawaz G, Rogol AD, Jenkins SM. Amenorrhea. [Updated 2024 Feb 25]. In: StatPearls [Internet].

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