Why Have I Missed My Menstrual Period?

Missing a period can be a stressful experience, especially if you’re unsure why it’s happening. While pregnancy is a common concern, there are many other reasons why you may have a missed period. As a sports dietitian specializing in Relative Energy Deficiency in Sport (RED-S) and Hypothalamic Amenorrhea (HA), I often see active women struggling with disruptions in their menstrual cycles. In this blog, we’ll explore potential causes, including female health, energy availability, stress, and hormonal imbalances.

Missing a period can be due to many reasons- this blog will explore potential issues which could cause this effect

Common Reasons for a Missed Period

1. Relative Energy Deficiency in Sport (RED-S) & Low Energy Availability

Low energy availability is one of the most common reasons for a missed menstrual period in female athletes and active individuals. This occurs when your body isn’t getting enough fuel to meet both training and essential bodily functions. When energy intake is consistently low, the hypothalamus reduces hormone production, disrupting menstrual cycle such as Hypothalamic Amenorrhea (HA).

Signs of RED-S & Low Energy Availability:

• Irregular or missed periods

• Decreased performance and recovery

• Increased risk of stress fractures and injuries

• Low libido and mood swings

  
  

2. Stress and Cortisol Overload

Chronic stress—whether from intense training, work, or personal life—can significantly impact female health. The body prioritizes survival over reproduction, meaning high cortisol levels can suppress ovulation and disrupt menstrual cycles.

Signs of High Stress Impacting Hormones:

• Fatigue and poor sleep

• Unexplained weight fluctuations

• Anxiety or irritability

• Frequent colds or infections

3. Hormonal Imbalances

Hormonal conditions such as Polycystic Ovary Syndrome (PCOS), thyroid dysfunction, or hypothalamic dysfunction can all contribute to a missed period. If your menstrual cycle is irregular or absent for several months, assessing underlying hormonal imbalances is essential.

Possible Hormonal Causes:

• PCOS: High androgens, irregular cycles, acne, weight fluctuations

• Thyroid Issues: Fatigue, hair thinning, temperature sensitivity

• Hypothalamic Amenorrhea: Low estrogen, low energy intake, excessive exercise

4. Weight Changes: Underweight or Overweight?

Significant weight loss or gain can lead to hormonal imbalances that disrupt your cycle. Low body fat levels (common in endurance athletes) can cause the body to shut down reproductive functions, while excessive weight gain may contribute to insulin resistance and hormonal dysregulation.

Considerations for Weight-Related Menstrual Disruptions:

• Have you recently lost or gained a significant amount of weight?

• Is your diet meeting your body’s energy demands?

• Are you over-exercising without proper recovery?

  
  

5. Overtraining and Excessive Exercise

While regular exercise supports female health, excessive training without adequate fuel can lead to Hypothalamic Amenorrhea. Women who engage in high-intensity training, such as running, cycling, or HIIT, are particularly at risk if they don’t consume enough calories.

How to Prevent Overtraining-Related Amenorrhea:

• Prioritize rest days

• Increase carbohydrate intake

• Reduce high-intensity training frequency

• Monitor changes in your cycle

  
  

What to Do If You Have a Missed Period

If you’re wondering, “Why have I missed my period?”, evaluating your lifestyle, nutrition, and stress levels is important. Here are some steps to help restore hormonal balance:

• Increase Energy Intake: Ensure you eat enough calories, particularly carbohydrates and healthy fats.

• Reduce Training Intensity: Scale back on high-intensity workouts and prioritize recovery.

• Manage Stress: Incorporate relaxation techniques such as meditation, deep breathing, and adequate sleep.

• Check Hormones: A blood test can assess thyroid function, estrogen, progesterone, and other key hormones.

• Seek Professional Support: A sports dietitian or endocrinologist can help address menstrual cycle disruptions and optimize your nutrition and training plan.

  
  

Jenaed Ruddock, Sports Dietitian, Specialist in Female Athlete Health, RED-S & Hypothalamic Amenorrhea

A missed period indicates that something may be off with your female health. Whether it’s RED-S, Hypothalamic Amenorrhea, stress, or hormonal imbalances, understanding the root cause is essential to restoring your cycle. If you’ve been missing periods for several months, it’s time to take action by adjusting your nutrition, training, and lifestyle.

If you need personalized support, book a consultation with me to help you regain hormonal balance and optimize your performance while maintaining a healthy menstrual cycle.