How late a period can be before it is considered delayed is generally at least 7 days, especially in people with regular menstrual cycles. A delay of more than 7 days can also be one of the earliest signs of pregnancy.
Early pregnancy may also cause implantation bleeding, which is light spotting that typically looks different from your usual period. Other early pregnancy symptoms usually appear 5 to 6 weeks after the first day of your last period. These can include nausea, vomiting, breast tenderness, and fatigue, along with a late period.
If your period is more than 7 days late and you think you may be pregnant, you can take a home pregnancy test or see your primary care provider for testing. Besides pregnancy, a late period can also be caused by stress, anxiety, weight changes, intense exercise, poor diet, certain medications, and conditions like hypothyroidism or polycystic ovary syndrome (PCOS).
If your period is consistently late or you are unsure about the cause, it is best to see a gynecologist or other women's health provider for evaluation.