What blood investigations are recommended for patients presenting with insomnia?

Blood Investigations for Insomnia

Blood investigations are not routinely indicated for the evaluation of chronic insomnia unless there is suspicion for comorbid disorders that may be contributing to sleep disturbance. 1

Initial Evaluation Approach

The evaluation of insomnia primarily relies on:

1. Clinical evaluation through thorough sleep history
2. Detailed medical, substance, and psychiatric history
3. Self-assessment tools

Recommended Assessment Tools

• A general medical/psychiatric questionnaire to identify comorbid disorders
• The Epworth Sleepiness Scale to identify sleepiness and comorbid disorders
• A two-week sleep log to identify sleep-wake patterns and variability 1

When Blood Tests Are Indicated

Blood investigations should only be performed when there is clinical suspicion of underlying medical conditions that may be causing or exacerbating insomnia. These situations include:

Medical Conditions That May Warrant Blood Testing

• Thyroid dysfunction: Consider thyroid-stimulating hormone (TSH) testing 2, 3
• Metabolic disorders: Consider glucose testing if symptoms suggest diabetes or hypoglycemia 2, 4
• Inflammatory conditions: Consider erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) 2
• Infectious diseases: Consider complete blood count (CBC) if symptoms suggest infection 2
• HIV-related conditions: Consider HIV testing if risk factors present 2
• Tuberculosis: Consider TB testing (PPD or interferon-gamma release assay) if night sweats, weight loss, or cough are present 2

Clinical Decision Algorithm

1. First step: Complete thorough sleep history and assessment tools
2. Second step: Evaluate for signs/symptoms of medical conditions
3. Third step: Order blood tests ONLY if specific medical conditions are suspected:
   • Thyroid function tests if symptoms of hypo/hyperthyroidism
   • CBC if infection or hematologic disorder suspected
   • Inflammatory markers if inflammatory condition suspected
   • Glucose testing if diabetes/hypoglycemia suspected
   • HIV testing if risk factors present
   • TB testing if classic symptoms present

Important Considerations

• Polysomnography and daytime multiple sleep latency testing are not indicated in routine evaluation of chronic insomnia 1
• Actigraphy may be indicated to characterize circadian rhythm patterns or sleep disturbances 1
• The presence of significant daytime sleepiness should prompt a search for other potential sleep disorders beyond insomnia 1
• Patients with normal polysomnography findings typically do not show impaired glucose tolerance despite insomnia symptoms 4

Common Pitfalls to Avoid

• Overreliance on laboratory testing: Insomnia is primarily diagnosed through clinical evaluation, not laboratory tests 1, 5
• Missing comorbid conditions: Failure to consider medical conditions that may contribute to insomnia can lead to ineffective treatment 1, 2
• Ignoring psychological factors: Focusing solely on physical causes while neglecting psychological contributors to insomnia 5
• Premature medication use: Jumping to pharmacological treatment before completing proper evaluation 5

Remember that cognitive behavioral therapy for insomnia (CBT-I) remains the first-line treatment for chronic insomnia, regardless of laboratory findings 5.