Causes of irregular periods include emotional stress, breastfeeding, excessive weight loss or gain, and eating disorders such as bulimia or anorexia, states WebMD. In rare cases, conditions such as liver disease, diabetes and irritable bowel syndrome can cause irregular periods.
Irregular periods are most common when a woman starts menstruating, and it may take several years before periods become regular, reports WebMD. Most women have between 11 and 13 menstrual periods in one year, and irregular periods may be a sign of perimenopause or menopause. Women are advised to practice birth control if they do not wish to have a baby, as a woman can still become pregnant even if she is not menstruating, notes WebMD.