The albumin/globulin (A/G) ratio is calculated by dividing your albumin level by your globulin level. A normal result is slightly above 1. If your lab report lists total protein and albumin but not globulin, you can still calculate it yourself with simple subtraction and division.
The Formula
The A/G ratio uses this equation:
A/G Ratio = Albumin ÷ Globulin
Most lab reports give you total protein and albumin directly, but globulin often isn’t listed as its own line item. To find it, subtract albumin from total protein:
Globulin = Total Protein − Albumin
Then divide albumin by that result. The units don’t matter as long as both numbers use the same ones (typically g/dL in the U.S. or g/L elsewhere), because they cancel out in the ratio.
A Worked Example
Say your lab report shows a total protein of 7.0 g/dL and an albumin of 4.0 g/dL. First, find globulin: 7.0 − 4.0 = 3.0 g/dL. Then divide: 4.0 ÷ 3.0 = 1.33. Your A/G ratio is 1.33, which falls in the normal range.
If instead your albumin were 3.2 g/dL and total protein were 8.0 g/dL, globulin would be 4.8 g/dL, and the ratio would be 3.2 ÷ 4.8 = 0.67. That’s below 1, which is considered low.
Where These Numbers Come From
Albumin and total protein are measured through a standard blood draw. They’re typically included as part of a comprehensive metabolic panel (CMP) or a liver function panel, both of which are common in routine checkups. A basic metabolic panel (BMP) does not include them, so if that’s the only test you had done, you won’t have the values you need.
Albumin is a single protein made by your liver. It keeps fluid balanced in your blood vessels and carries various substances through your bloodstream. Globulin is actually a catch-all category for dozens of different proteins, including immune system antibodies and proteins involved in blood clotting and inflammation. Because globulin represents so many different proteins lumped together, the A/G ratio is a broad screening tool rather than a precise diagnostic.
What a Normal Ratio Looks Like
A healthy A/G ratio is slightly above 1, meaning you have a bit more albumin than globulin in your blood. The exact cutoff varies slightly by lab, so check the reference range printed on your results. Most labs flag anything below 1.0 as low, though some use a range of roughly 1.0 to 2.5.
A ratio of exactly 1.0 means albumin and globulin are present in equal amounts. That’s borderline and may or may not be meaningful depending on context.
What a Low A/G Ratio Means
A low ratio (below 1.0) means globulin levels are relatively high compared to albumin. This can happen for two reasons: your body is producing less albumin, your body is producing more globulin, or both.
Conditions associated with a low A/G ratio include:
- Liver disease, including cirrhosis. The liver makes albumin, so damage to the liver can reduce albumin production and drag the ratio down.
- Kidney disease. Damaged kidneys can leak albumin into the urine, lowering the amount in your blood.
- Autoimmune diseases such as lupus. These conditions ramp up immune activity, which increases the production of antibodies (a type of globulin).
- Chronic infections or inflammation. Prolonged immune responses raise globulin levels.
- Certain blood cancers, such as multiple myeloma, where abnormal immune cells produce large amounts of a single globulin protein.
A low ratio on a single test doesn’t diagnose any of these conditions. It signals that something may be off with protein balance, and your provider will typically order follow-up tests to pinpoint the cause.
What a High A/G Ratio Means
A high ratio is less common and generally less discussed. It indicates that globulin levels are unusually low relative to albumin. This can occur with certain genetic immune deficiencies where the body doesn’t produce enough antibodies. Some types of leukemia can also suppress globulin production. In practice, a high A/G ratio is flagged less frequently than a low one, and your provider will evaluate it alongside other markers on your panel.
Factors That Can Skew the Result
Because the A/G ratio depends on protein concentrations in your blood, anything that changes the fluid balance in your bloodstream can shift the numbers. Dehydration concentrates all proteins, which can artificially raise both albumin and globulin and make the ratio appear normal even when it isn’t. Overhydration does the opposite, diluting protein levels.
A very high-protein diet doesn’t directly change albumin or globulin levels in a clinically meaningful way, since the liver and immune system regulate these proteins independently of dietary protein intake. However, recent intense exercise, pregnancy, and certain medications (particularly steroids and hormonal treatments) can influence the results. If your ratio comes back borderline, your provider may retest under controlled conditions before drawing conclusions.