This plasma osmolality calculator takes the figures you already have and applies the relationship behind plasma osmolality calculations for you, giving plasma osmolality from blood urea nitrogen, glucose and sodium.
What Is the Plasma Osmolality Calculator?
The plasma osmolality calculator gives you an estimate of plasma osmolality based on blood urea nitrogen, glucose and sodium.
It is a quick reference figure rather than a diagnosis, and it is most useful for tracking how a number moves over time rather than for interpreting a single reading.
How the Plasma Osmolality Estimate Is Worked Out
The calculation follows published reference relationships, so it is a reasonable approximation when the inputs are accurate. It assumes an average adult and does not account for individual variation.
If you are comparing two people, or the same person over a period of weeks, keep the method and the inputs identical. A change in the method can easily look like a change in the person.
What This Calculator Does Not Do
It does not diagnose anything, and it does not replace advice from a clinician. If a figure comes out at an extreme, or if it differs sharply from what you expect, that is a reason to speak to a professional rather than to adjust the inputs.
Nothing you type here is stored or sent anywhere. The whole calculation happens in your browser.
A Worked Example
Working through an example, with blood urea nitrogen set to 10, glucose set to 5, sodium set to 2, the calculator returns plasma osmolality of 7.84921. Substitute your own figures and the same steps produce the same kind of answer.
Frequently Asked Questions
What do I need to work out plasma osmolality?
Enter blood urea nitrogen, glucose and sodium. The calculator then works through the relationship and reports plasma osmolality.
What does the plasma osmolality actually calculate?
It takes blood urea nitrogen, glucose and sodium and converts them into plasma osmolality using the standard relationship for this problem. Each step is applied in turn, so every output is traceable back to the numbers you typed in.
How should I enter blood urea nitrogen?
Use the value you actually have, in the unit shown next to the field. Enter every value in the same unit system. The calculator assumes the figures you supply are consistent, so it cannot correct a mistake that happens before the calculation starts.
Does anything you type get stored?
No. The whole calculation runs inside your browser, and nothing you enter is uploaded, logged or sent anywhere.
Is the answer exact?
It is as exact as the formula and the inputs allow. The method itself is the standard one for this problem, so the only sources of error are the figures you enter and the precision you ask for.