Bicarbonate

Bicarbonate (HCO₃⁻) is your blood’s main base and a key part of the body’s acid–base buffering system. It is closely related to carbon dioxide (CO₂), and most CO₂ that is in the body exists as bicarbonate. Together, your lungs (which control CO₂) and kidneys (which reabsorb or excrete bicarbonate) use it to keep blood pH in a tight, healthy range. Because most CO₂ in the blood is stored as bicarbonate, the number you see on an electrolyte panel largely reflects this bicarbonate pool and your overall acid–base balance.

When bicarbonate runs low, it suggests the body is carrying extra acid. Even when mild and symptom-free, long-term low bicarbonate is linked with faster decline in kidney function, loss of muscle and bone, and higher risk of adverse outcomes in people with chronic kidney disease (CKD).

In the general population, low bicarbonate (<22 mmol/L) and high levels (>26 mmol/L) have each been associated with higher cause-specific mortality in large datasets, hinting that “too low” and “too high” may both carry risk over time. High bicarbonate can also reflect compensation for long-standing lung conditions such as COPD or sleep-disordered breathing, or due to diuretics or vomiting. Tracking this marker over the long term helps you see whether your lifestyle is moving your acid–base balance in the right direction.

If bicarbonate is high:

High bicarbonate levels may occur due to overuse of alkali supplements, certain medications, or underlying health conditions.

• Avoid excessive intake of bicarbonate-rich supplements or mineral waters unless specifically advised by a healthcare provider.

• Monitor for symptoms such as muscle twitching, confusion, or irregular heartbeat, and report these to a healthcare professional.

• Maintain a balanced diet with moderate protein intake and avoid unnecessary restriction of fruits and vegetables, as these foods support overall health without excessively raising bicarbonate.

• Regular blood tests may be needed to monitor bicarbonate and related markers, especially in people with kidney disease.

If bicarbonate is low:

Low bicarbonate levels can be a sign of metabolic acidosis, which is common in chronic kidney disease and may contribute to muscle loss, bone health problems, and faster progression of kidney disease.

• Eating more alkaline-rich foods — such as fruits and vegetables — can help raise bicarbonate levels and reduce acid load.

• Plant-based diets (like Mediterranean or vegetarian patterns) have been shown to improve bicarbonate and kidney function, and are generally safe.

• Bicarbonate-rich mineral water may also help support acid-base balance. Limit foods high in animal protein and processed foods, which increase acid load and may lower bicarbonate.

• If dietary changes are not enough, medications such as sodium bicarbonate may be prescribed by a medical practitioner, but should be monitored to avoid raising bicarbonate too high.

• Regular follow-up and blood tests are important to track progress and adjust treatment as needed.

• Optimal: 22 to 29

• Mildly low: 18 to 21

• Very low: <18

• Mildly high: 30 to 32

• Very high: ≥33
  

Low values often reflect metabolic acidosis, while high values may reflect metabolic alkalosis or compensation for chronic CO₂ retention. Always interpret alongside other electrolytes and (when needed) blood gases.

1. Kidney Failure Risk Factor: Serum Bicarbonate, National Kidney Foundation, 2025. Available from: https://www.kidney.org/kidney-failure-risk-factor-serum-bicarbonate

2. Bicarbonate, Clinical Biochemistry Test Catalogue, Oxford University Hospitals NHS Foundation Trust, 2025. Available from: https://www.ouh.nhs.uk/biochemistry/tests/tests-catalogue/bicarbonate/

3. The Beneficial Effects of Fruits and Vegetables on Kidney Disease and Related Disorders, The American Journal of Medicine, 2024. Available from: https://www.amjmed.com/article/S0002-9343(24)00486-8/fulltext

4. A Comparison of Treating Metabolic Acidosis in CKD Stage 4 with Fruits and Vegetables or Sodium Bicarbonate, Clinical Journal of the American Society of Nephrology (CJASN), 2013. Available from: https://europepmc.org/articles/PMC3586961/

5. Serum Bicarbonate Concentration and Cause-Specific Mortality: The NHANES 1999–2010, Mayo Clinic Proceedings, 2020. Available from:https://www.mayoclinicproceedings.org/article/S0025-6196(19)30625-1/fulltext