Normal Serum Bicarbonate Range
The normal range for serum bicarbonate in adults is 22-26 mmol/L, with values below 22 mmol/L indicating metabolic acidosis requiring treatment and values persistently above 26 mmol/L associated with increased cardiovascular risk. 1
Standard Reference Range
Serum bicarbonate measured on a Basic Metabolic Panel (BMP) represents total CO2 content, which includes bicarbonate (HCO3-), dissolved CO2, and other minor carbon dioxide components, with bicarbonate comprising approximately 96% of the total. 2
The physiologically optimal range is 22-26 mmol/L, which represents the target for maintaining metabolic homeostasis and preventing complications. 1
Clinical Significance of Values Outside Normal Range
Low Bicarbonate (<22 mmol/L)
Values below 22 mmol/L indicate metabolic acidosis and are associated with adverse outcomes including protein catabolism, bone demineralization, CKD progression, and increased mortality risk. 3, 1
Multiple guidelines recommend oral bicarbonate supplementation when serum bicarbonate falls below 22 mmol/L to maintain levels within the normal range, unless contraindicated. 3
In CKD patients, each 1 mmol/L increase in serum bicarbonate within the normal range is associated with reduced risk of death, dialysis, or GFR decline (hazard ratio 0.942). 4
Severe acidosis with bicarbonate <18 mmol/L requires aggressive pharmacological intervention, representing a medical emergency. 1
High Bicarbonate (>26 mmol/L)
Persistent serum bicarbonate >26 mmol/L is associated with increased risk of heart failure (HR 1.66; 95% CI 1.23-2.23) and mortality (HR 1.36; 95% CI 1.02-1.82) in CKD patients. 5
Values >27 mmol/L should prompt evaluation for chronic respiratory acidosis with renal compensation, particularly in obese patients where arterial blood gas measurement may be needed to confirm hypercapnia. 2, 6
Avoid over-correction of bicarbonate levels, as metabolic alkalosis is associated with worse outcomes in heart failure; target maintenance at 22-26 mmol/L, not supranormal values. 1
Monitoring Recommendations by Clinical Context
Chronic Kidney Disease
Measure serum bicarbonate at least annually in patients with GFR 30-59 ml/min/1.73 m² (CKD Stage 3) and at least twice yearly in patients with GFR <30 ml/min/1.73 m² (CKD Stages 4-5). 3
Maintain serum bicarbonate ≥22 mmol/L through oral supplementation (typically 2-4 g/day or 25-50 mEq/day of sodium bicarbonate divided into 2-3 doses) to prevent CKD progression and bone disease. 3, 1
Post-Kidney Transplant
- Monitor serum bicarbonate levels frequently following transplantation, with measurement frequency based on time post-transplant and clinical stability. 3
Critical Clinical Caveats
Each gram of sodium bicarbonate contains approximately 12 mEq of sodium, requiring careful consideration in patients with heart failure, hypertension, or volume overload. 1
Distinguish metabolic from respiratory causes of abnormal bicarbonate; obtain arterial blood gas if uncertainty exists about the primary acid-base disturbance. 1
Recognize diuretic-induced alkalosis (elevated bicarbonate from volume depletion and chloride loss), which should be treated with volume repletion with normal saline or acetazolamide, not additional bicarbonate. 1
Avoid citrate-containing alkali salts in CKD patients exposed to aluminum, as citrate increases aluminum absorption. 3