My Period Used To Be Regular. Why Is It Suddenly Changing Now?

It can feel unsettling when your period, which was always regular, suddenly becomes unpredictable. Maybe it came earlier than usual, got delayed by several days, became heavier or lighter, or changed in flow or duration. Period changes can bring a lot of confusion and worry, especially if you have always had a stable cycle.

The truth is that your menstrual cycle reflects your body’s internal balance. Even small shifts in hormones, lifestyle, or health can create sudden changes. The good news is that most of these reasons are common and treatable.

This guide breaks down why your period may have changed, what your body is trying to tell you, and when to consult a doctor.

Understanding How Your Menstrual Cycle Works

A normal menstrual cycle is usually between 24 to 35 days. Your body prepares for a possible pregnancy through hormonal changes controlled by the brain, ovaries, and uterus. If anything affects this hormonal chain, your period can shift.

When your period suddenly becomes irregular, it usually means one of three things:

• Your hormones have fluctuated

• Your lifestyle has changed

• Your body is under physical or emotional stress

Understanding the root cause can help you feel more in control.

Common Reasons Your Period Suddenly Changed

Here are the most common causes women experience when their cycle, once regular, becomes unpredictable.

1. Stress and emotional changes

Stress is one of the biggest triggers of sudden period irregularity. When you are stressed, your brain releases hormones that interfere with ovulation. If ovulation gets delayed, your period gets delayed too.

Stress can come from:

• Work pressure

• Exams

• Family or relationship changes

• Lack of sleep

• Emotional burnout

You may also notice mood swings, headaches, or disturbed sleep along with the change in your cycle.

2. Weight gain or weight loss

Your body fat percentage directly affects hormone production. Sudden changes in weight can disturb the menstrual cycle.

Common patterns include:

• Weight gain causing delayed or missed periods

• Weight loss leading to lighter or shorter periods

• Intense exercise affecting ovulation

Even a 3 to 5 kg change can influence your cycle.

3. Thyroid issues

Your thyroid gland controls metabolism and hormones. When it becomes underactive or overactive, your period can change suddenly.

Signs may include:

• Fatigue

• Hair fall

• Dry skin

• Weight changes

• Feeling too cold or too hot

Thyroid-related period changes are very common and easily diagnosable with a simple blood test.

4. Hormonal imbalance or PCOS

Even if you never had irregular periods before, PCOS can show up later in life. It is a condition where your body produces slightly higher levels of male hormones, affecting ovulation.

Signs include:

• Acne

• Hair fall or facial hair growth

• Weight gain

• Irregular or missed periods

• Difficulty losing weight

PCOS does not always show symptoms early, so many women get diagnosed only when periods start becoming unpredictable.

5. Change in sleep pattern

Your hormones follow a biological clock. When your sleep cycle is disturbed, your period cycle can get disturbed too.

Triggers include:

• Night shifts

• Staying awake late

• Travelling across time zones

• Irregular sleep timing

Poor sleep affects the hormones responsible for ovulation, which can delay your period.

6. Birth control changes

If you recently started, stopped, or changed your birth control method, your period may shift temporarily.

Common changes include:

• Lighter periods

• No periods

• Irregular spotting

• Heavier flow in the first cycles after stopping pills

Your body usually adjusts in a few months.

7. Excess exercise or intense workouts

Working out is healthy, but over-exercising can lower the hormones needed for ovulation. Women who suddenly increase workout intensity may see their periods become lighter or delayed.

Activities like:

• Running

• CrossFit

• HIIT

• Weightlifting

can impact the menstrual cycle if the body is not getting proper rest and nutrition.

8. Perimenopause

Women in their late 30s or early 40s may notice changes in their period due to perimenopause, which is the transition phase before menopause. The cycle may become shorter, longer, heavier, or lighter.

Common signs include:

• Night sweats

• Mood swings

• Sleep disturbances

• Sudden hot flashes

Period changes may be one of the first signs.

9. Illness or fever

Your body prioritizes recovery when you are sick. A recent infection, flu, stomach illness, or fever can temporarily shift your menstrual cycle.

10. Medications

Certain medications can affect your hormones, including:

• Antidepressants

• Thyroid medications

• Steroids

• Antipsychotics

If your cycle changed after starting a new medicine, this could be the reason.

11. Pregnancy

If your period is late, even by a few days, pregnancy cannot be ruled out. Some women still get light bleeding around the time of their missed period, which they confuse for a change in cycle.

If you are sexually active, it is always worth taking a test.

12. Post-infection or post-COVID hormonal changes

Many women have reported cycle changes after viral infections, including COVID. Fever and immunity shifts can affect hormones for several weeks.

Signs You Should Not Ignore

While most period changes are harmless, some symptoms need attention:

• Very heavy bleeding

• Bleeding lasting more than a week

• Bleeding between periods

• Severe pain

• Persistent irregular periods

• Periods stopping for more than 2 to 3 months

These symptoms do not always mean something serious, but they should be evaluated.

What Doctors Usually Check

To understand the cause of your cycle change, a doctor may recommend:

• Thyroid test

• Hormonal profile

• Ultrasound

• Pregnancy test

• CBC for anemia

• Blood sugar levels

These tests help identify if the issue is hormonal, lifestyle-based, or medical.

How to Support Your Body Naturally

While you evaluate the cause, simple steps can help regulate your cycle.

Maintain a balanced weight

Keep a steady diet and avoid extreme weight changes.

Manage stress

Try relaxation practices, breathing exercises, or mindful breaks during the day.

Sleep consistently

Sleep and wake up at the same time daily.

Nourish your body

Ensure you eat enough protein, iron, healthy fats, and vitamins.

Avoid over-exercising

Stay active but give your body enough rest.

Track your cycle

Use a simple app to note changes and patterns.

When Should You See a Doctor?

You should consult a gynecologist if:

• Your period was regular and suddenly becomes irregular

• The changes continue for more than two cycles

• You have other symptoms like severe acne, hair fall, or weight gain

• You feel anxious about the change

• Your period stops completely

A quick evaluation can help clear confusion and give you peace of mind.

Final Thoughts

A regular period suddenly becoming irregular can feel unsettling, but it is usually your body’s way of telling you that something has changed. Whether it is stress, hormones, sleep, weight, or a medical condition, understanding the cause is the first step toward restoring balance. With the right guidance and care, your cycle can return to normal, and you can feel more in control of your health again.