Irregular periods: causes and what to do

According to MedlinePlus, periods usually come every 21 to 35 days and last about 4 to 7 days. Every body is different: in teens, cycles can vary more in the first few years, and in your 40s periods may start to change.

Get checked if your period comes less than 21 days after the last one or takes longer than 35, if the time between periods changes every month, if it lasts more than 7 days, if you bleed between periods or after sex, or if you have missed more than one period.

MedlinePlus explains that the most common reason a period stops is pregnancy. If you have had sex, take a home pregnancy test. We do not provide pregnancy care: if it is positive, contact an OB-GYN. If it is positive and you have severe belly pain, bleeding, shoulder pain or feel faint, go to the emergency room right away: it could be an ectopic pregnancy.

The table on this page sums up the most common causes. According to MedlinePlus:

• Normal changes: breastfeeding, the first years after your first period, and perimenopause. See menopause.
• Birth control: the pill, patch, ring, shot or hormonal IUD can change or stop bleeding, and periods can take months to return after stopping. See birth control.
• Stress, a lot of exercise or big weight changes.
• PCOS: irregular periods with acne, extra hair growth or insulin resistance. See PCOS.
• Thyroid: both an overactive and an underactive thyroid can change your periods. See hyperthyroidism and hypothyroidism.
• Other causes: high prolactin, some medicines, fibroids or polyps in the uterus and, less often, ovary problems.

You see Dr. Diana Nieves Castro, MD, a Puerto Rico–licensed general practice physician with several years of emergency-department experience, in English or Spanish. She asks when your last period was, what your cycles have been like, whether you use birth control, how heavily you bleed, and whether you have acne, extra hair growth, tiredness, a racing heart or weight changes.

We evaluate, diagnose and treat. If needed, we give you a lab order for a lab near you. Depending on your case, MedlinePlus lists tests such as a pregnancy test, thyroid (TSH), prolactin, other hormones and a blood count if you bleed heavily. We go over the results with you in a follow-up visit. If appropriate, the doctor prescribes and we send your prescription to your pharmacy. If you need an ultrasound or a pelvic exam, we refer you.

If you are under 21, your parent or legal guardian must be on camera for the whole visit and show photo ID.

A doctor visit costs US$79, the same price for every age. Request a visit online 24/7 — we confirm your time by email or text.

MedlinePlus advises checking any unexplained bleeding between periods and any bleeding after menopause. Most causes are benign and treatable, but sometimes something more serious has to be ruled out. If you have gone 12 months without a period and start bleeding again, we refer you for an in-person evaluation with gynecology.

For your safety, go to the emergency room or call 911 if you have:

• Bleeding so heavy you soak a pad or tampon every hour for 2 hours or more
• Severe dizziness or fainting
• Severe belly pain, shoulder pain or bleeding with a positive pregnancy test