Diagnostic Approach to Metallic Taste

Zopiclone/eszopiclone is consistently associated with metallic or bitter taste, occurring in 7-26% of patients, making it one of the most common medication-related causes 1
Local anesthetics can cause metallic taste as an early sign of systemic toxicity, accompanied by circumoral numbness and facial tingling 2

Systemic Medical Conditions

Hematological disorders, particularly polycythemia vera, can present with generalized pruritus and metallic taste 3
Chronic kidney disease can lead to aluminum toxicity, which may manifest as metallic taste 4
COVID-19 infection has been associated with taste disturbances, including metallic taste 5

Complete blood count (CBC) with blood film to evaluate for hematological disorders, particularly polycythemia vera 3
Comprehensive metabolic panel to assess kidney and liver function 4
Erythrocyte sedimentation rate (ESR) to screen for inflammatory conditions 3
Serum aluminum levels if aluminum toxicity is suspected, particularly in patients with chronic kidney disease, with baseline levels <20 μg/L 4
Consider deferoxamine (DFO) test if serum aluminum levels are 60-200 μg/L 4
JAK2 V617F mutation analysis if polycythemia vera is suspected 3

For patients with suspected COVID-19, appropriate testing should be performed 5
If medication-related dysgeusia is suspected, a thorough medication review should be conducted 1
Blood sampling should be performed before meals, as food intake can affect certain biomarkers 6
Patients should refrain from smoking or consuming nicotine products for at least 4 hours before blood sampling 6
No alcohol consumption should occur in the 12 hours preceding blood collection 6
Dental work within 1-2 hours of blood sampling should be avoided to minimize blood contamination 6
Recent acute infections, especially upper respiratory tract infections within the past 2 weeks, should be noted as they may affect results 6

If initial blood work is inconclusive but symptoms persist, consider referral for specialized taste testing using standardized methods such as "Sniffin' Sticks" or other validated olfactory/gustatory assessment tools 7, 8
In cases of persistent unexplained metallic taste, consider evaluation for neurological disorders that may affect taste perception 8