Blood vs. Gastric Juice pH: Why Blood Is Alkaline and Stomach Acid Is Not

Blood pH: 7.35–7.45 (slightly alkaline)
Gastric Juice pH: ~1.5–2.0 (highly acidic)

Comparison

• Blood is ~10⁵ to 10⁶ times less acidic than gastric juice.
• Blood buffers (bicarbonate, phosphate, proteins) maintain a tight, life-sustaining range.
• Stomach acid (HCl) serves digestion, pathogen killing, and B₁₂ release.

Physiological Separation

The gastric mucosal barrier, bicarbonate secretion, and rapid emptying prevent acid from damaging systemic circulation. Pancreatic bicarbonate neutralizes chyme in the duodenum.

Clinical Relevance

• Blood pH disturbances (acidosis/alkalemia): Cause multi-organ dysfunction.
• Gastric acid disorders: GERD, peptic ulcer disease, Zollinger-Ellison syndrome.