I had some bloodwork done and my albumin was 21. what is albumin, and what does this mean?

Probably lab error: Albumin is a protein made by the liver and is measured through blood testing. It is usually used as a marker of nutrition or liver disease. Normal values are generally between 3.5 to 5. The value of 21 is unusually high and is most likely an error.

Blood protein: Albumin is a protein, produced by the liver, that is found in the blood. It does a lot of stuff including carrying drugs and other stuff around as well as maintaining the correct osmotic pressure in your blood. As a blood test, it is a measure of liver function. The doc who ordered the blood tests should explain the results to you at your next encounter.