What Affects the Feeling of Low Energy
Low energy and fatigue result from a complex interplay of medical, psychological, behavioral, and lifestyle factors that must be systematically evaluated and addressed.
Primary Medical Causes
The most critical treatable medical conditions to evaluate include:
- Thyroid dysfunction is among the first and most important causes to investigate, as hypothyroidism frequently presents with fatigue and nonspecific symptoms 1
- Anemia occurs in approximately 2.8% of patients presenting with tiredness and requires evaluation through complete blood count and iron studies 2, 1
- Cardiac dysfunction should be assessed, particularly in patients with cardiovascular risk factors or those who received cardiotoxic treatments 1
- Nutritional deficiencies including vitamin B6, B12, folate, ferritin, zinc, vitamin D, magnesium, copper, phosphate, and calcium can all contribute to fatigue 1, 3
Psychological and Emotional Factors
Mental health conditions are major contributors that are frequently overlooked:
- Depression affects 18.5-33% of patients with fatigue and is significantly more frequent among those complaining of tiredness compared to those without this symptom 2, 1, 3
- Anxiety frequently accompanies fatigue and requires specific assessment 2, 4, 1
- Emotional distress can both cause and exacerbate fatigue symptoms 2, 4
Sleep-Related Factors
Sleep disturbances are a neglected but critical problem:
- Sleep disorders ranging from hypersomnia to insomnia affect 30-75% of patients with fatigue 2, 4, 1
- Poor sleep hygiene including irregular sleep schedules, daytime napping, and consumption of caffeine or alcohol before bed contributes significantly to fatigue 2, 4
- Sleep apnea can develop as a consequence of surgery affecting the upper airway, changes in body composition, or alterations in hormone status 2
Medication and Substance Effects
Pharmaceutical and substance-related causes are common but often missed:
- Medication side effects including sedation are frequent contributors to fatigue 2, 4, 1
- Alcohol and substance use patterns, particularly binge drinking that creates recovery cycles, should be systematically evaluated 2, 3
- Thyroid hormone overtreatment can paradoxically cause fatigue along with other symptoms of hyperthyroidism 5
Physical Activity and Lifestyle
Activity patterns have a bidirectional relationship with fatigue:
- Decreased physical activity worsens fatigue symptoms, while regular physical activity reduces the risk of experiencing low energy (odds ratio = 0.61; 95% CI 0.52,0.72) 4, 1, 6
- Body mass index and waist circumference show a U-shaped association with fatigue, with healthiest measurements associated with feeling "fresh" rather than tired 7
- Insufficient physical activity makes tired or exhausted participants 1.9 to 3.8 times more likely to report inadequate exercise compared to those feeling fresh 7
Pain and Concurrent Symptoms
Fatigue rarely occurs in isolation:
- Pain often clusters with fatigue and requires effective treatment as part of comprehensive management 2, 4
- Fatigue seldom occurs alone and more commonly clusters with sleep disturbance, emotional distress, or pain 2, 4
Chronic Disease and Comorbidities
Underlying medical conditions significantly impact energy levels:
- Chronic diseases including cardiovascular disease, pulmonary dysfunction, and inflammatory conditions contribute to persistent fatigue 2, 8
- Disease activity in chronic inflammatory conditions can cause fatigue even when in remission or low disease states 2
Critical Clinical Pearls
Important considerations for evaluation and management:
- Laboratory results affect management in only about 5% of fatigue cases, but core testing remains essential to rule out treatable causes 4, 1, 9
- Overlooking psychological causes such as depression and anxiety leads to inadequate treatment 4, 1
- Missing sleep disorders results in incomplete management 4, 1
- Ignoring medication side effects can perpetuate fatigue unnecessarily 4, 1