What causes persistent fatigue and low mood?
Quick answer: Persistent fatigue, brain fog, mood swings, and poor sleep are commonly driven by nutrient deficiencies, blood sugar dysregulation, adrenal stress, thyroid dysfunction, or gut health imbalances. A naturopathic approach investigates all potential drivers rather than treating symptoms in isolation.
Fatigue and mood disturbances are the most common concerns I see in clinic. What makes them challenging is that they’re rarely caused by a single factor — more often, it’s a combination of hormonal, nutritional, metabolic, and nervous system imbalances that have built up over time.
Many clients come to me after being told their blood work is “normal” despite feeling exhausted, flat, or anxious. Standard testing often doesn’t capture the full picture — iron studies, thyroid panels, vitamin D, B12, and cortisol patterns all need to be assessed comprehensively to understand what’s actually driving the symptoms.
How do you differentiate between the causes of fatigue?
Adrenal and HPA axis dysfunction: Chronic stress disrupts the hypothalamic-pituitary-adrenal axis, leading to cortisol dysregulation. This often presents as “wired but tired” — exhausted during the day but unable to wind down at night. Research shows that prolonged cortisol elevation impairs hippocampal function, contributing to brain fog, poor memory, and mood instability (Herbert, 2013, Neuroimmunomodulation).
Thyroid dysfunction: Even subclinical hypothyroidism — where TSH is within “normal” range but suboptimal — can cause significant fatigue, weight gain, brain fog, and low mood. I routinely request full thyroid panels including Free T3, Free T4, and thyroid antibodies rather than relying on TSH alone.
Iron deficiency: One of the most common nutritional deficiencies in women, and frequently missed because ferritin isn’t always included in standard testing. Optimal ferritin for energy is above 50 μg/L — well above the “normal” lower limit on most lab ranges. Low iron directly impairs oxygen transport and cellular energy production.
Gut-brain axis: Around 95% of serotonin is produced in the gut. Gut dysbiosis, inflammation, and impaired digestive function directly affect neurotransmitter production, contributing to low mood, anxiety, and poor cognitive function (Carabotti et al., 2015, Annals of Gastroenterology).
Blood sugar dysregulation: Erratic blood sugar causes energy crashes, irritability, anxiety, and afternoon fatigue. Many clients don’t realise that their dietary patterns — skipping meals, relying on caffeine, high refined carbohydrate intake — are directly destabilising their energy and mood throughout the day.
What does your assessment process look like?
In your 90-minute initial consultation, I assess your full health history, energy patterns throughout the day, sleep quality, stress load, menstrual cycle, diet, and digestive function. I then recommend targeted blood work to fill in the gaps — typically including iron studies, full thyroid panel, vitamin D, B12, folate, and fasting glucose.
My treatment approach addresses the specific drivers identified: targeted supplementation for nutrient deficiencies, herbal adaptogens for adrenal support (such as Withania and Rhodiola), dietary strategies to stabilise blood sugar, gut support where indicated, and sleep and stress management strategies. Most clients notice meaningful improvement within four to six weeks of starting their plan.
References: Herbert, J. (2013). Cortisol and depression: three questions for psychiatry. Psychological Medicine, 43(3), 449–469. Carabotti, M., et al. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of Gastroenterology, 28(2), 203–209.