Osmolal Gap Calculator

Formula

The formula to calculate the Osmolal Gap (OG) is:

\[ OG = \text{Measured Osmolality} - \text{Calculated Osmolality} \]

Where:

OG is the Osmolal Gap
Measured Osmolality is the osmolality measured in a laboratory
Calculated Osmolality is calculated using the formula: \(2 \times (\text{Na}^+) + \left(\frac{\text{Glucose}}{18}\right) + \left(\frac{\text{BUN}}{2.8}\right)\)

What is an Osmolal Gap?

The Osmolal Gap is a diagnostic tool used in medicine to identify the presence of certain toxins in the body. It is the difference between the measured osmolality (the concentration of solutes in the blood) and the calculated osmolality. A higher than normal Osmolal Gap can indicate the presence of toxins such as methanol, ethylene glycol, or isopropyl alcohol in the blood.

Example Calculation

Let's assume the following values:

Measured Osmolality: 300
Sodium (Na+) Concentration: 140
Glucose Concentration: 90
Blood Urea Nitrogen (BUN) Level: 15

Step 1: Calculate the Calculated Osmolality:

\[ \text{Calculated Osmolality} = 2 \times 140 + \left(\frac{90}{18}\right) + \left(\frac{15}{2.8}\right) = 280 + 5 + 5.36 = 290.36 \]

Step 2: Subtract the Calculated Osmolality from the Measured Osmolality:

\[ 300 - 290.36 = 9.64 \]

The Osmolal Gap (OG) is 9.64.