Irregular periods: is it normal — and what could be causing variation?

If your menstrual cycle doesn't follow a predictable schedule, it's easy to feel unsure or worried. Many people are raised to believe there's one "correct" cycle length, but that's not the case. Periods come in a range of lengths, and variation from one cycle to the next is often normal.

Irregular periods — where the length of cycles, timing, or flow changes more than expected — are common and usually reflect how responsive the menstrual cycle is to hormones, stress, lifestyle, and life stage. In many cases, irregularity is not a sign of serious disease but an indication of how your body is balancing internal and external influences.

Tools like Rhyva can help you understand these shifts over time instead of treating each cycle as a mystery. By stepping back and focusing on understanding what's normal for your period, patterns across phases and symptoms become clearer and more informative.

What counts as an irregular period?

A menstrual cycle is typically considered irregular when:

• Timings vary significantly from one month to the next
• Cycle length is much shorter (e.g., <21 days) or much longer (e.g., >35 days) than usual
• Periods are sometimes missing or infrequent
• The pattern of bleeding changes unpredictably, including spotting between periods

Some health sources define irregular cycles as varying by more than 20 days between cycles or falling outside typical ranges. Even so, variation is common, especially during puberty and perimenopause.

What causes irregular periods?

There isn't a single cause — many factors can contribute, and most are hormonal, lifestyle-related, or linked to life stage.

Hormonal fluctuations (common and normal)

Your menstrual cycle depends on a balance of hormones like oestrogen and progesterone. If those hormones shift, the timing of ovulation — and therefore your period — can change too, which is often why people start wondering why their period might be late.

Stress and emotional load

Stress triggers higher cortisol levels, which can interfere with hormones that regulate menstruation. This can delay or disrupt ovulation, leading to irregular cycles, missed periods, or changes in flow.

Lifestyle changes

Changes in:

• Sleep patterns
• Nutrition or weight (both gain and loss)
• Exercise routines (especially heavy training)
• Travel or illness

can impact hormone regulation and cycle timing. Intense exercise, very low calorie intake, or significant weight changes can shorten, lengthen, or suppress your cycle entirely.

Contraception and medication

Hormonal birth control methods — including pills, implants, patches, and hormonal IUDs — directly affect ovulation and bleeding patterns. It's common to have irregular bleeding, spotting, or skipped periods after starting or stopping these methods. Other medications (like steroids, antidepressants, or antiepileptic drugs) can also affect hormone balance and cycle regularity.

Life stage transitions

Periods are often most variable during:

• Adolescence: cycles can take years to settle into a pattern.
• Post-pregnancy or breastfeeding: hormonal shifts can delay regular cycles.
• Perimenopause: hormone levels fluctuate more dramatically, leading to irregular cycles years before periods stop.

These variations often look irregular but are a normal part of your body's changing hormonal landscape.

Less common but important causes

Sometimes irregular periods are due to underlying health conditions, including:

Polycystic Ovary Syndrome (PCOS)

PCOS is a common condition where hormonal imbalances interfere with ovulation, leading to infrequent or irregular periods. It may also be associated with other symptoms like acne, weight changes, or unwanted hair growth.

Thyroid dysfunction

Both hyperthyroidism and hypothyroidism (overactive or underactive thyroid) can disrupt menstrual cycles by interfering with hormone regulation.

Reproductive conditions

Conditions like endometriosis, uterine fibroids, or pelvic inflammatory disease may cause bleeding changes or irregular cycles.

Nutritional or energy imbalances

Eating disorders, extreme dieting, nutrient deficiencies, or significant energy deficits can impact reproductive hormones and lead to irregular cycles or even amenorrhea (absent periods).

Irregular cycles can also come with changes in how you feel, such as fatigue, nausea, or bloating — symptoms that are often experienced as period symptoms when you're not pregnant.

When irregular periods are usually normal

Irregular cycles are often considered normal when they:

• Occur occasionally rather than all the time
• Are linked to stress, lifestyle, or life transitions
• Don't include worrying symptoms like severe pain or very heavy bleeding
• Gradually resolve on their own over time

Some people also notice that irregular cycles come with cramping or pelvic discomfort, including painful periods despite normal scans. Patterns matter more than moment-to-moment changes.

When it might be worth checking in

While many causes of irregular periods are harmless, it's helpful to talk to a healthcare professional if:

Your provider may suggest tests — such as bloodwork, ultrasound, or hormonal panels — to look for underlying conditions or imbalances.

Rhyva and cycle awareness

Irregular periods make far more sense when you look at your full cycle context — not just the bleeding. Many people find that tracking how symptoms, timing, stress, and lifestyle all interact gives them insight that feels grounding instead of confusing.

This is core to how Rhyva supports menstrual understanding — not by telling you what should happen, but by helping you see what is happening across time.

Frequently asked questions

Key takeaways

• Irregular periods are common and often influenced by hormones, stress, lifestyle, or life stage.
• Most irregular patterns are not serious but worth understanding in context.
• Health conditions can sometimes contribute and are worth checking if symptoms are persistent or severe.
• Seeing patterns over time — not just month to month — gives you clarity.