What Causes Irregular Periods and Abnormal Menstrual Bleeds?

Many women experience irregular periods—cycles that are really long, too short, or unpredictable. While irregular periods are common, they can also be frustrating, especially when you’re unsure of the cause. 

Irregular menstrual cycles often point to underlying issues like hormonal imbalances, lifestyle factors, or health conditions. By understanding the potential causes, you can take the first step toward finding answers. This blog will explore the most common reasons for irregular periods and what might be happening in your body. For insights on how to manage or treat these irregularities, take a look at my other blog posts focused on treatment strategies. 

What Is an Irregular Period? 

An irregular period is any menstrual cycle that falls outside the “normal” range of 21-35 days or varies significantly in length month-to-month. Abnormal bleeding can also take many forms: 

• Short cycles (less than 21 days) or long cycles (more than 35 days). 

• Periods lasting fewer than 3 days or more than 7 days. 

• Spotting or bleeding between periods. 

Irregular periods can be a signal from your body that something is out of balance, whether it’s hormones, lifestyle, or a health condition. Identifying the root cause is the key to restoring regularity and supporting overall health. 

Ovulation: The Main Event of the Menstrual Cycle 

At the heart of a healthy menstrual cycle is ovulation—the release of a mature egg from the ovary. This is the event that makes a woman fertile and allows for the possibility of conception. Ovulation drives the production of progesterone, a hormone that stabilises the uterine lining and regulates the second half of your cycle. 

Without ovulation, the body does not produce progesterone, which can lead to irregular or unpredictable periods. Many of the causes of irregular cycles, such as stress, thyroid issues, or PCOS, stem from anovulation (the absence of ovulation). Understanding whether ovulation is occurring is essential for uncovering the reason behind your cycle irregularities. 

The Role of Hormones in Menstrual Cycle Irregularities 

1. Oestrogen and Progesterone Imbalance 

Oestrogen and progesterone are the two primary hormones driving the menstrual cycle. Oestrogen dominates the first half, helping to build the uterine lining, while progesterone stabilises it in the second half. 

• Low Oestrogen: Can cause short, light periods or missed cycles. 

• Low Progesterone: May result in spotting, prolonged bleeding, or a luteal phase (the second half of your cycle) that is too short. 

• High Oestrogen: Excess oestrogen (often called “oestrogen dominance”) can cause heavy or prolonged bleeding, mood swings, and bloating. 

2. Prolactin 

Prolactin, the hormone responsible for milk production after pregnancy, can also affect menstrual cycles when elevated (a condition called hyperprolactinemia). High prolactin levels suppress ovulation and can lead to irregular or absent periods. Other symptoms are low libido and pain during sex caused by vaginal dryness. Causes include stress, pituitary disorders, low thyroid function, or medications like antidepressants. 

3. Cortisol and Stress 

Chronic stress can disrupt the hypothalamic-pituitary-ovarian (HPO) axis, leading to cycle irregularities. Elevated cortisol levels suppress ovulation, potentially resulting in delayed or missed periods. In some cases, stress may even shut down menstruation altogether, a condition known as hypothalamic amenorrhea. 

Lifestyle Factors Affecting Menstrual Cycles 

1. Under-Eating and Over-Exercising 

When your body doesn’t get enough energy to meet its needs, it prioritises survival over reproduction. This can suppress ovulation, leading to irregular or absent periods. 

2. Anovulation 

Cycles without ovulation can cause irregular bleeding patterns, heavier periods, or longer cycles. Sometimes, anovulation causes bleeding that may appear to be a period but isn’t. Anovulation is often linked to hormonal imbalances caused by factors like stress, PCOS, or thyroid dysfunction. 

Underlying Health Conditions That Cause Irregular Periods 

1. High Histamine 

Histamine, a compound involved in immune responses, can influence oestrogen levels. Elevated histamine levels may lead to heavier or more painful periods. If you experience symptoms like headaches, allergies, eczema or digestive issues alongside irregular cycles, histamine intolerance could be a factor. 

For more information about histamine read my post Histamine Intolerance and its Effects on Hormones and Period Health.

2. PCOS (Polycystic Ovary Syndrome) 

PCOS is one of the most common causes of irregular periods, characterised by high androgen levels, infrequent ovulation, and insulin resistance. It often results in long cycles, missed periods, or heavy bleeding. 

3. Perimenopause 

In the years leading up to menopause, hormone fluctuations can result in irregular cycles, spotting, or skipped periods. This transition can begin in the mid-to-late 30s and is a natural part of aging. 

4. Hypothyroidism 

An underactive thyroid affects the HPO axis, leading to long or heavy cycles. Other symptoms of hypothyroidism include fatigue, cold intolerance, and weight gain. 

5. Celiac Disease 

Celiac disease, an autoimmune disorder, disrupts nutrient absorption, which can impact hormones and lead to irregular periods. Undiagnosed celiac disease may result in missed periods, anaemia, or infertility. 

When to Seek Help 

If irregular periods are interfering with your life, it’s important to seek professional guidance. Consider consulting a healthcare provider if: 

• Your cycles are consistently irregular. 

• Bleeding lasts more than 7 days or is extremely heavy. 

• You miss periods for more than 3 months without pregnancy. 

• Severe pain, fatigue, or other unusual symptoms are present. 

A healthcare professional can help identify the underlying cause of your irregular periods and guide you toward effective solutions. 

Irregular periods are often a sign that your body is trying to tell you something. Whether it’s due to hormonal imbalances, lifestyle factors, or an underlying condition, understanding what’s happening in your body means you can begin to uncover the root cause and take steps toward balance. 

If you’d like more information on the root causes of your period and hormone related symptoms, check out my free guide Hormone Imbalances: Understanding and Interpreting Symptoms. 

I can support you with figuring out what’s driving your irregular periods and natural treatments to regulate your cycle. Book a free discovery call to have a chat about it.