What Causes Irregular Periods? 8 Factors You Might Not Have Considered
- Gemma Knaap
- Sep 8
- 3 min read
Having a period that’s unpredictable, skipping altogether, or arriving too soon or too late each month can feel frustrating — especially if you’re trying to understand your cycle, manage symptoms, or support your fertility. Irregular periods are incredibly common, but they’re also a sign that your body needs something — whether that’s stress support, nourishment, or hormonal rebalancing.
What Counts as an “Irregular” Period?
While no two person's menstrual cycles are exactly the same, a healthy cycle typically falls between 24 to 35 days, with less than 7 days’ variation from month to month.
A cycle is considered irregular if:
It’s shorter than 24 days or longer than 35 days
The timing varies widely each month
You miss periods entirely
Your bleeding is unusually heavy or light
You experience spotting between cycles
8 Common (and Overlooked) Causes of Irregular Periods
1. Stress and Cortisol
Chronic stress affects your hypothalamic-pituitary-ovarian (HPO) axis — the communication system that governs ovulation and menstruation.High cortisol levels can delay or suppress ovulation, leading to long, short, or missed cycles. If your periods changed during or after a stressful life event, this is probably a key driver for you.
2. Undereating or Low Energy Availability
Whether intentional or not, not eating enough can reduce GnRH signalling and shut down ovulation. This is common in athletes, dieters, or busy women skipping meals.
Look for:
Low appetite, fatigue, or feeling cold often
Loss of period (amenorrhoea)
Weight loss or nutrient deficiencies
3. PCOS (Polycystic Ovary Syndrome)
PCOS is one of the most common causes of irregular cycles — especially cycles longer than 35 days. Don't be fooled by the name — PCOS is often driven by insulin resistance, androgen excess, or inflammatory patterns, even in lean women. You don't even need to have cysts on your ovaries to be diagnosed with PCOS.
Other signs may include:
Acne or hair growth on face/chest
Irregular or absent periods
Difficulty managing weight or blood sugar
4. Thyroid Dysfunction
Both hypothyroidism and hyperthyroidism can disrupt menstrual regularity.
Low thyroid (hypothyroidism): can cause heavy, delayed, or missed periods
Overactive thyroid (hyperthyroidism): may lead to lighter, more frequent bleeding
If you have fatigue, sensitivity to cold, hair thinning, or heart palpitations, thyroid function should be checked.
5. Perimenopause
In your late 30s and 40s, cycles may begin to shift due to declining ovarian function — even if periods appear normal some months.
Signs include:
Cycles getting shorter, longer, or more erratic
PMS worsening
Mid-cycle spotting or skipped ovulation
This is a normal transition but can be supported through nutrition and hormone-aware strategies.
6. Coming Off Hormonal Birth Control
After stopping the pill, IUD, or implant, it may take time for ovulation and regular cycles to return — especially if periods were irregular before starting.
Some women experience:
Post-pill amenorrhoea (no period)
Spotting, acne, or cycle fluctuations for months
Gentle support can help re-establish your natural hormonal rhythm.
7. Gut and Inflammation Issues
Emerging research links gut health to the endocrine system. Chronic gut inflammation, dysbiosis, or food intolerances can affect hormone metabolism and ovulation.
If you have digestive symptoms alongside cycle irregularity, this may be a driver for you.
8. Nutrient Deficiencies
Ovulation depends on adequate levels of:
Zinc, B6, and magnesium
Iron and vitamin D
Healthy fats (for hormone production)
Low intake or poor absorption (e.g. in coeliac disease or post-antibiotics) can interfere with cycle function.
What Should You Do if Your Periods Are Irregular?
Start by tracking your cycle: Use an app or paper tracker to record cycle length, symptoms, flow, and mood.
Look for patterns: Has something changed recently — diet, stress, sleep, illness, or medication?
Test, don’t guess: Thyroid panels, nutrient screening, and hormone testing may help uncover the root cause.
Irregular Periods Are a Sign — Not a Diagnosis
Your period is one of your body’s most honest feedback systems. When something is off, your cycle reflects that — often before other symptoms show up. Instead of masking irregular periods with the pill or waiting it out, the best approach is to gently support your body’s systems: nourishment, stress recovery, gut health, and blood sugar balance.
🌿 If your cycle feels unpredictable and you’re not sure where to begin, I offer 1:1 consults to help uncover the root cause and guide your return to regular, healthy menstruation.
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