1. Sudden weight loss
When your body mass index (BMI) drops below 18-19, it is possible that you can have late periods or skipped periods. This doesn't mean that only those who suffer from serious illnesses like bulimia or anorexia can experience this, but also those who are training for a major sporting event or any other event where you are exercising more than usual and reducing body weight.
Your hypothalamus and pituitary gland regulate your oestrogen cycle and are highly susceptible to stress and cortisol under what is known as the hypothalamic-pituitary-adrenal axis. If there has been a major event in your life or you are stressed about something that is highly important to you, it is not unusual for cortisol to begin taking its effect on your body, including on the hypothalamus, causing irregularities in your period
3. Polycystic Ovary Syndrome (PCOS)
PCOS is a common disorder in women of the reproductive age. Although the exact cause is still unknown, it can be one of the reasons for having irregular periods or a late period. Other symptoms of PCOS include excessive hair growth, acne, obesity and enlarged ovaries that contain fluid-filled sacs.
4. Your birth control pill
It is perfectly normal whilst on some low dose birth control pills to experience a late period (this would be a welcomed effect, for most!). Even when you stop the pill, it can take a few months in some cases for your period to return to normal, but it is certainly not abnormal.
Information sourced from Mayo Clinic online. Image sourced from Chelsey Dyer