Why Are My Periods
Suddenly Irregular?

What counts as an irregular period?

A typical menstrual cycle runs anywhere between 21 and 35 days. If your cycle has always been 28 days and suddenly becomes 40, that counts as irregular. If your periods come at completely unpredictable times with no pattern, that also counts. Occasional variation of a few days here and there is completely normal and not something to worry about.

The key question is not just the timing, but whether something has changed from your usual pattern.

Common reasons periods go off schedule

Most of the time, a temporarily irregular cycle has a straightforward explanation. Here are the most common ones:

• Stress is the single most common cause. High stress raises cortisol, which interferes with the hormones that trigger ovulation. Exams, grief, a new job, a difficult relationship. All of these can delay your period by days or even weeks.
• Significant weight changes in either direction can disrupt the hormonal signals your brain sends to your ovaries. This is especially true if your weight has changed quickly.
• Poor or disrupted sleep affects your hormonal rhythms more than most women realise. Night shifts, long-haul travel, and irregular sleep patterns can all show up as cycle changes.
• Intense exercise, particularly when combined with undereating, can suppress ovulation. This is common in athletes and women who have recently started vigorous training.
• Travel and time zone changes can temporarily throw off your cycle, especially if they involve significant disruption to your routine.
• Starting or stopping hormonal contraception almost always causes temporary irregularity while your body readjusts.
• Illness, even a relatively minor infection, can sometimes push back ovulation and delay your period.

When should you actually see a doctor?

A single late or missed period after an obvious stressful event is not usually cause for alarm. But do make an appointment if:

• Your periods have been irregular for three months or more with no clear explanation
• You are missing periods entirely (not due to pregnancy)
• Your cycle is shorter than 21 days or longer than 35 days consistently
• Your periods have become very heavy, very light, or significantly more painful than before
• You are trying to conceive and have irregular cycles
• You have other symptoms alongside the irregularity: hair loss, unusual hair growth, acne, weight changes, or fatigue

What tests are usually done?

When you see a gynecologist about irregular periods, the first appointment is mostly a conversation. Your doctor will ask about your cycle history, any recent lifestyle changes, stress levels, other symptoms, and your family history.

If investigation is needed, it usually starts with a few simple blood tests to check your hormone levels including FSH, LH, prolactin, TSH (thyroid), and sometimes AMH. A pelvic ultrasound is also commonly done to look at the ovaries and uterine lining. These tests are not invasive and give a lot of information quickly.

Common myths worth clearing up

Myth: Irregular periods mean you cannot get pregnant. Not necessarily. Many women with irregular cycles ovulate perfectly well, just at unpredictable times. That said, irregular ovulation can make conception harder to time, which is worth discussing with your doctor if you are trying.

Myth: You need to have a period every 28 days. The 28-day cycle is an average, not a rule. Cycles between 21 and 35 days are completely normal.

Myth: If it was regular before, it will stay regular forever. Your cycle changes throughout your life, after illness, pregnancy, weight changes, medication, and especially in your 30s and 40s as your hormone levels naturally begin to shift.

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This article is for general information only and is not a substitute for medical advice. If you have concerns about your menstrual health, please book a consultation with a qualified gynecologist.