| Substance | Extracellular | Intracellular | |
| E | Na+ | 140 mmol/L | 10 mmol/L |
| I | K+ | 4 mmol/L | 140 mmol/L |
| E | Ca2+ (free) | 2.5 mmol/L | 0.1 micromol/L |
| I | Mg2+ | 1.5 mmol/L | 30 mmol/L |
| E | Cl- | 100 mmol/L | 4 mmol/L |
| E | HCO3- | 27 mmol/L | 10 mmol/L |
| I | PO4 | 2 mmol/L | 60 mmol/L |
| E | Glucose | 5.5 mmol/L | 0-1 mmol/L |
| I | Protein | 2g/dL | 16g/dL |
NB:
Intracellular pH = 6.8-7.1
Reference range for serum [Mg2+]
= 0.7 to 1.0 mmol/L
= 1.4 to 2.0 mmol/L
* [KB2:p17]