Studio Portrait Of Stressed Teenage GirlMissed or late periods happen for many reasons other than pregnancy. Common causes can range from hormonal imbalances to serious medical conditions.

Menstrual periods last anywhere from two to seven days and the average cycle is once every 28 days, although it can vary. Anywhere between 24 and 35 days is considered a normal cycle. If your cycle is usually regular and you’re suddenly late having your period, it can be a worry.

If you are not pregnant, other causes of missed or irregular periods include:

1. Weight – If you’re underweight, your body won’t produce the hormones it needs to complete a menstrual cycle.  If you’re overweight, your hormones may be thrown out of whack and make it hard to conceive.  Having too low of a body fat percentage is unhealthy and you may experience a missed period.  You need to be at a healthy weight in order to maintain a normal hormonal balance.

2. Stress – If you’ve had a busy schedule or a family trauma, it can delay your period. Ironically, if you’ve had unprotected sex and are worrying about the possibility of pregnancy, the stress can stop your period and make you think you’re pregnant when you’re not.

3. Illness – Being sick at the time you normally would ovulate can delay ovulation — and if you ovulate late, you’ll get your period late. So if your period hasn’t arrived on schedule, think back a few weeks — were you under the weather?

4. Polycystic Ovary Syndrome – PCOS is a hormone imbalance that comes down to a lack of ovulation, so you have altered levels of estrogen, progesterone, and testosterone. It can cause you to completely miss your period or just not menstruate regularly. Other PCOS symptoms include hair growth in places like the face and chest, difficulty losing weight, and potential fertility issues.

5. Your cycle might be irregular from month to month – This means that last month your cycle might have been 24 days long, and this month it could be 32 days long. When your period doesn’t show up when it’s expected, it could be because your body hasn’t finished its cycle yet.

6. Birth Control – You may experience a change in your cycle when you go on or off birth control. Birth control pills contain the hormones estrogen and progestin, which prevent the ovaries from releasing eggs. It can take up to six months for your cycle to become consistent again after stopping the pill. Other types of contraceptives that are implanted or injected can cause missed periods as well.

If you’ve taken a negative pregnancy test and your period is more than a couple weeks late, you should see your gynecologist just to make sure everything is OK.