American Board of Internal Medicine (ABIM) Certification Practice Exam

Question: 1 / 2705

Which calculation is used for serum osmolality?

2Na + BUN/1.5 + glucose/12

2Na + BUN/4 + glucose/20

2Na + BUN/2.8 + glucose/18

The calculation for serum osmolality is derived from the concentrations of sodium, blood urea nitrogen (BUN), and glucose in the blood. The most widely accepted formula is:

Serum Osmolality = 2(Na) + (BUN/2.8) + (glucose/18)

Using this equation, the sodium concentration is multiplied by 2, reflecting the contribution of sodium ions to osmolality, which is significant given that sodium is a major extracellular cation. The BUN value is then divided by 2.8 to account for its contribution to osmotic pressure, and glucose is divided by 18, appropriately reflecting its impact on serum osmolality.

In this context, the correct answer includes the appropriate divisions for both BUN and glucose, making it the accurate option for calculating serum osmolality. Understanding the specific values for BUN and glucose is essential to obtaining an accurate osmolality measurement as both substances contribute to the overall osmotic pressure in the bloodstream.

Get further explanation with Examzify DeepDiveBeta

2Na + BUN/3 + glucose/15

Next Question

Report this question

Download American Board of Internal Medicine (ABIM) Certification Practice Exam PDF Study Guide
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy