Lab values and concentrations

This course is a part of Health and medicine, a 22-course Topic series from Khan Academy.

Ever wonder about your lab values and what they mean? Lab values measure amounts of electrolytes, metabolites, proteins or cells in your blood and occasionally tell you about how hormones and enzymes are working! Dive deeper and expand your understanding of concentration units used in common medical lab values as well!

This course contains 10 segments:

Introduction to lab values and normal ranges

Find out how health professionals use short-hand for labs and the meaning of normal ranges. Rishi is a pediatric infectious disease physician and works at Khan Academy.

What's inside of blood?

Spin down your blood and find out what it's made up of. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Units for common medical lab values

Figure out how to interpret the units in common medical labs including the CBC, Chem 10, and LFTs. Rishi is a pediatric infectious disease physician and works at Khan Academy.

What is an equivalent?

Figure out how to calculate an equivalent and how it relates to a mole. Rishi is a pediatric infectious disease physician and works at Khan Academy.

The mole and Avogadro's number

One mole of a substance is equal to 6.022 × 10^23 units of that substance (such as atoms, molecules, or ions). The number 6.022 × 10^23 is known as Avogadro's number or Avogadro's constant. The concept of the mole can be used to convert between mass and number of particles.

Molarity vs. molality

Learn how molarity and molality differ! The molality of a solution is equal to the moles of solute divided by the mass of solvent in kilograms, while the molarity of a solution is equal to the moles of solute divided by the volume of solution in liters. For example, a 1 molal solution contains 1 mole of solute for every 1 kg of solvent, while a 1 molar solution contains 1 mole of solute for every 1 L of solution.

Molarity vs. osmolarity

Molarity and osmolarity may sound similar, but they are two distinct concepts. Molarity (M) is the number of moles of solute per liter of solution. The unit of molarity is the mole (mol). Osmolarity (Osm/L) is the total concentration of all solutes in the solution. The unit of osmolarity is the osmol (osm). Osmolarity can be used to predict whether water will move from one side of a semipermeable membrane to the other.

Calculate your own osmolarity

Learn how to use three lab values (Sodium, glucose, and BUN) to approximate your plasma osmolarity. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Molarity, molality, osmolarity, osmolality, and tonicity - what's the difference?

See how each of these terms tells us something different about a solution. Rishi is a pediatric infectious disease physician and works at Khan Academy.

Tonicity - comparing 2 solutions

Find out how tonicity is determined by ions that don't move across membranes and how it affects the movement of water. Rishi is a pediatric infectious disease physician and works at Khan Academy.