Normal Uric Acid Levels
Normal serum uric acid levels are generally considered to be below 6.0 mg/dL (360 μmol/L) for both men and women, though traditional reference ranges have been higher for men (up to 7.2 mg/dL) and postmenopausal women compared to premenopausal women (up to 6.0 mg/dL). 1
Gender-Based Reference Ranges
Traditional laboratory reference ranges have typically used the following values:
- Men: 3.5-7.2 mg/dL
- Premenopausal women: 2.6-6.0 mg/dL
- Postmenopausal women: Similar to men (3.5-7.2 mg/dL)
However, these ranges are being reconsidered based on clinical outcomes rather than population distributions alone.
Clinical Significance of Uric Acid Levels
Risk Stratification
- Levels above 6.0 mg/dL (360 μmol/L) are associated with increased risk of gout development, regardless of gender 1
- Even levels between 5.0-6.0 mg/dL may carry increased cardiovascular and hypertension risk 2
- The risk of developing gout increases significantly with higher uric acid levels:
- Men with levels >6 mg/dL have over 4 times higher risk of developing gout
- Women with levels >6 mg/dL have 17 times higher risk of developing gout 1
Important Considerations
- Serum uric acid levels can be misleadingly normal during acute gout attacks, as uric acid can behave as a negative acute phase reactant 1, 3
- Up to 63.3% of patients with acute gout attacks may have normal serum uric acid levels 3
- Most laboratories calculate their own reference ranges based on the mean plus two standard deviations from their local healthy population, calculated separately for men and women 1
Revised Thinking on "Normal" Levels
Recent evidence suggests that the traditional reference ranges may need revision:
- A threshold value <6.0 mg/dL (<360 μmol/L) appears to better identify truly "healthy subjects" regardless of gender 4
- This level is below the theoretical saturation point for monosodium urate (MSU) crystals
- Values within the traditional "normal" range may still be associated with:
- Silent deposition of MSU crystals
- Increased risk of hypertension
- Metabolic syndrome (particularly in males) 5
Clinical Applications
When interpreting uric acid levels:
- Consider 6.0 mg/dL as a clinically relevant threshold for both genders
- Be aware that "normal" levels don't exclude gout, especially during acute attacks
- For patients on urate-lowering therapy, the target is typically <6.0 mg/dL 6
- For patients with tophaceous gout, a lower target of 5.0 mg/dL may be appropriate
Risk Factors for Elevated Uric Acid
- Medications (thiazide and loop diuretics, low-dose aspirin, calcineurin inhibitors)
- Genetic factors affecting renal transporters of urate
- Dietary factors (high fructose intake, purine-rich foods, alcohol)
- Renal impairment
- Obesity and features of metabolic syndrome 7
Pitfalls in Interpretation
- Acute gout attacks: Uric acid levels may be normal or even low during acute attacks due to increased renal excretion 1, 3
- Time of measurement: Levels should ideally be measured during intercritical periods for diagnostic purposes
- Hydration status: Dehydration can artificially elevate uric acid levels
- Medications: Many medications can affect uric acid levels
In conclusion, while traditional reference ranges have varied by gender, current evidence suggests that a universal threshold of <6.0 mg/dL represents a more clinically relevant "normal" range for both men and women, with values above this level associated with increased risk of gout and potentially other health conditions.