Chronic fatigue can feel overwhelming, especially when you don’t know what’s causing it. Many people assume it’s “just stress,” but persistent exhaustion often has underlying medical or sleep‑related causes. Two of the most common contributors are sleep disorders (like obstructive sleep apnea or insomnia) and hormonal imbalances (like thyroid issues).
Let’s look at how these causes differ, what symptoms to look for, and which steps help you get clarity faster.
What Causes Chronic Fatigue? The Two Most Common Causes
Most long‑term fatigue comes from one (or both) of these categories:
1. Sleep‑Related Causes
Lack of restful sleep affects your brain, mood, metabolism, and immune system. The most common sleep issues linked to fatigue include:
- Obstructive Sleep Apnea (OSA): OSA happens when the airway repeatedly collapses during sleep, causing reduced airflow. Common signs include loud or habitual snoring, waking up gasping, morning headaches, daytime sleepiness, or concentration issues.
- Insomnia (Difficulty Falling or Staying Asleep): Insomnia isn’t just about having a bad night’s sleep, it’s ongoing difficulty sleeping despite adequate opportunity to sleep. It can lead to low energy, mood changes, trouble focusing, irritability, or feeling unrefreshed.
Individuals with insomnia or insomnia symptoms may benefit from Cognitive Behavioural Therapy for Insomnia (CBT‑I).
2. Hormonal or Nutrient Deficiencies
These issues can mimic sleep deprivation, even if you’re technically sleeping enough.
- Thyroid Issues (Hypothyroidism): When the thyroid is underactive, your body slows down. Common symptoms include fatigue, weight gain, sensitivity to cold, or dry skin.
- Iron Deficiency, Low B12 & Vitamin D Deficiency: Low iron, B12, or Vitamin D can impact how your body produces energy and regulates mood. When these levels are low, you may experience symptoms such as fatigue, weakness, shortness of breath, low mood, or dizziness.
- Menopause & Perimenopause: Hormonal fluctuations can disrupt sleep and energy.
Sleep Disorders vs Hormonal Causes: Key Differences
| Sleep-Related Fatigue | Hormonal Fatigue |
| Waking unrefreshed | Fatigue even after “sleeping well” |
| Snoring, choking, gasping | Weight or temperature changes |
| Difficulty falling or staying asleep | Changes tied to menstrual cycle or aging |
| Frequent nighttime awakenings | Mood swings, anxiety, irritability |
| Morning headaches or dry mouth | Dizziness, weakness, or paleness |
Many people have both, which is why screening is helpful. Learn more in our blog on Understanding Insomnia & the Screening Process or contact us if you’d like to schedule a consultation.
Frequently Asked Questions
This often indicates that the sleep you’re getting isn’t restful. Issues such as snoring, OSA, or insomnia can affect sleep quality even when sleep quantity seems normal.
Lifestyle changes can help, but if the underlying cause is sleep‑related or hormonal, proper screening and evaluation are key.
Obstructive sleep apnea is one of the most common sleep disorders linked to chronic fatigue. It involves repeated airflow interruptions during sleep, making rest less restorative.
If you snore, feel sleepy during the day, wake up unrefreshed, or have frequent awakenings, a sleep screener can help determine whether a sleep test may be appropriate.