Osmolar Gap
Note: normal serum osmolarity is 280 to 300.
Osmolar gap = calculated osmolarity - actual osmolarity
Calc osm=
2Na + glucose/18 + BUN/2.8
Can round off:
2Na +glucose/20 +BUN/3
Increased in:
If the hx does not suggest either lactic acidosis or ketoacidosis, then a high osmolal gap, esp if > 25 suggest methanol or ethylene glycol intox.