The protein block on a metabolic or liver panel is four rows deep and contains fewer measurements than that.
What the rows are
MedlinePlus describes total protein directly: "This test measures the total amount of protein in your blood, which includes albumin and globulins. These proteins are mainly made in your liver."
So total protein is the sum of two families, and the report typically prints all of it:
Total protein — everything.
Albumin — "a protein made in the liver", per MedlinePlus, and the single largest component.
Globulin — the remainder: not one protein but a family of them, grouped together.
A/G ratio — albumin divided by globulin.
Which are measured
Laboratories commonly measure total protein and albumin directly. Globulin then comes from subtraction — total minus albumin — and the A/G ratio is a division of the two values above it.
That makes two of the four rows arithmetic. Reports sometimes mark them; often they do not.
Why it matters that globulin is a difference
For the same reasons as indirect bilirubin, which is derived the same way.
Globulin inherits the measurement variation of both inputs. It cannot move on its own — if it changed, total protein or albumin changed, and the explanation is on the same page. And a report that omits it has left nothing out, because it can be recovered.
The A/G ratio compounds this: it is a ratio of a measured value to a derived one, so it moves in response to either input and does not by itself say which.
Why globulin is not a single substance
Worth being explicit, because the row's name implies otherwise. Globulins are a group of proteins with different jobs, reported as one number because the number is obtained by subtraction rather than by measuring any particular one.
A test that separates them exists and is a different test — it is not what this row is.
Reading the block
Start with the two measured values. If total protein and albumin are both stable across reports, globulin and the ratio are stable by construction; if one of them moves, the movement in the derived rows is a consequence rather than a second finding.
As everywhere, use the reference interval printed on the report the value came from — derived rows especially, since they depend on which values that laboratory measured directly.