8 Common Causes You Should Know

Published by Pure Health Primary Care on April 5, 2026

Noticing Changes in Your Cycle?

Your menstrual cycle is an important sign of overall health.

If your periods have become:

• unpredictable
• more frequent or farther apart
• heavier or lighter than usual
• completely absent for a time

it may reflect a temporary hormonal shift — but it can also point to an underlying issue that deserves attention.

Irregular periods are common, but they are not always something to ignore.

What Is Considered a Normal Cycle?

For many adults, a typical menstrual cycle occurs about every 21 to 35 days, and bleeding usually lasts up to 7 days.

Some variation can happen from time to time. What matters most is whether your pattern has changed noticeably or whether bleeding has become unusually heavy, prolonged, or difficult to predict.

8 Common Causes of Irregular Periods

1. Stress

Physical or emotional stress can affect the brain-hormone signals that regulate ovulation. This may lead to delayed periods, missed periods, or changes in flow.

2. Polycystic Ovary Syndrome (PCOS)

PCOS is a common hormonal condition that can cause:

• irregular or absent periods
• acne
• increased facial or body hair
• difficulty with ovulation

3. Thyroid Disorders

Both an underactive and overactive thyroid can affect menstrual regularity. Thyroid dysfunction may also cause fatigue, hair changes, weight changes, or temperature intolerance.

4. Weight Loss, Weight Gain, or Over-Exercise

Significant changes in weight, restrictive eating, or very intense exercise can disrupt ovulation and lead to missed or irregular periods.

5. Perimenopause

As hormone levels begin to fluctuate in the years leading up to menopause, cycles often become less predictable. Periods may come closer together, farther apart, heavier, lighter, or be skipped.

6. Pregnancy

Pregnancy should always be considered when a period is missed or significantly delayed, especially if you are sexually active.

7. Birth Control Changes

Starting, stopping, or switching contraception can temporarily change bleeding patterns. Some methods also make periods lighter or absent altogether.

8. Other Medical Conditions

Irregular bleeding can also be associated with other health concerns, including elevated prolactin, uncontrolled diabetes, uterine polyps or fibroids, and less commonly, disorders affecting the lining of the uterus.

When to Seek Medical Care

It is a good idea to book an assessment if:

• your periods suddenly become irregular after previously being predictable
• you miss 3 periods in a row and pregnancy is not the explanation
• your bleeding lasts longer than 7 days
• your periods are very heavy
• you bleed between periods or after sex
• you also have symptoms such as pelvic pain, fatigue, acne, weight changes, or fertility concerns

Why Proper Assessment Matters

Many patients assume irregular periods are “just hormones” and wait it out.

Sometimes that is true — but sometimes irregular bleeding is the first clue that something else is going on.

Assessment may involve reviewing your cycle history, pregnancy testing when appropriate, medication review, and targeted blood work or imaging depending on your symptoms and risk factors.

How Pure Health Primary Care Can Help

At Pure Health Primary Care, we provide evidence-based assessment and individualized care for menstrual health concerns.

• Review of symptoms and menstrual pattern
• Pregnancy and hormonal evaluation when appropriate
• Investigation for common underlying causes
• Treatment recommendations based on diagnosis and goals

Your symptoms are valid — and changes in your cycle deserve proper assessment.

Take the Next Step Toward Better Health

If your periods have become irregular, an early assessment can help identify the cause and guide the right treatment.

Phone: 613-908-8999

Email: info@pureclinic.ca

Website: pureclinic.ca

This article was reviewed by Agnes Etaka, Nurse Practitioner at Pure Health Primary Care.

This article is for educational purposes only and does not replace medical advice or an individual clinical assessment.