Periods aren’t always textbook-perfect — a little variation from month to month is common. But when cycles become consistently irregular, unusually heavy, absent, or painful, it’s worth paying attention. Changes in your menstrual cycle can be a sign of stress, yes — but they can also reflect underlying hormonal imbalances or health conditions that deserve investigation.

At Zenvité, we help women understand their cycles, identify potential causes of irregularity, and use targeted blood testing to build personalised care plans. Here’s what you need to know.

What Counts as an Irregular Cycle?

A “normal” menstrual cycle typically lasts between 21 and 35 days, measured from the first day of one period to the first day of the next. Variation of a few days is normal, but cycles are considered irregular if they:
Consistently fall outside this range
Vary widely from month to month (e.g. 28 days one cycle, 45 the next)
Are absent for more than three months (amenorrhoea)
Are unusually frequent (less than 21 days apart) or infrequent (more than 35 days apart)

Common Causes of Irregular Periods

1. Stress and Lifestyle Factors

The hypothalamic-pituitary-ovarian (HPO) axis that regulates your cycle is sensitive to:

• Emotional stress

• Significant weight changes

• Overexercising

• Poor sleep patterns

These factors can suppress ovulation temporarily, leading to irregularity.

2. Polycystic Ovary Syndrome (PCOS)

PCOS is one of the most common causes of irregular cycles, affecting up to 1 in 10 women. Signs include:
Irregular or absent periods
Excess hair growth (hirsutism) or acne
Weight gain or difficulty losing weight

Blood tests often reveal elevated androgens (male hormones) or markers of insulin resistance.

3. Thyroid Disorders

Both underactive (hypothyroidism) and overactive (hyperthyroidism) thyroid glands can disrupt menstrual cycles. Other signs may include changes in energy, mood, weight, or hair.

4. Perimenopause

In your 40s (sometimes earlier), fluctuating oestrogen and progesterone levels can make cycles irregular as the body transitions toward menopause.

5. Other Hormonal Imbalances

Conditions like hyperprolactinaemia (high prolactin levels) or adrenal disorders can also interfere with normal ovulation.

When to Seek Help

It’s time to speak with a doctor if you experience:
Cycles shorter than 21 days or longer than 35 days
Periods missed for more than three months (without pregnancy)
Very heavy bleeding (soaking through a pad/tampon hourly)
Severe pain disrupting daily life
Other symptoms like unexplained weight changes, hair thinning, or acne

Early evaluation helps identify any underlying issues and guides the best course of action.

What Blood Tests Can Reveal

Blood tests provide insight into your hormonal landscape and help pinpoint potential causes of irregularity.

Common Tests Include:

FSH and LH – to assess pituitary function and ovarian reserve
Oestradiol (Oestrogen) – to check ovarian activity
Progesterone – to confirm ovulation (usually measured ~7 days before an expected period)
Testosterone and Androgens – to check for PCOS or other androgen excess
Thyroid Function Tests (TSH, T4) – to rule out thyroid disorders
Prolactin – high levels can suppress ovulation
HbA1c or Fasting Insulin – to assess for insulin resistance in PCOS

Timing of tests is important: some are best done on specific days of the cycle (e.g. day 2–5 for baseline hormones, day 21 for progesterone).

How Zenvité Supports Women With Irregular Cycles

At Zenvité, we provide:
Comprehensive hormone testing tailored to your cycle and symptoms
Lifestyle medicine advice for nutrition, stress, and sleep to support hormonal balance
Private GP consultations for diagnosis and personalised care plans
Referral to specialists (e.g. gynaecologists, endocrinologists) if needed

Our holistic approach looks beyond symptoms to understand your unique biology.

Listen to Your Body’s Signals

Irregular periods aren’t something you have to “put up with.” They’re a valuable signpost from your body, pointing to areas that may need support.

Book a private consultation with Zenvité today to explore what’s driving your cycle changes — and start your journey to hormonal balance.