Albumin blood test: what it measures, normal levels, and what low albumin (hypoalbuminemia) means

Albumin makes up more than half of the protein in blood plasma. The liver produces it continuously, and each molecule circulates for about three weeks. Its two jobs explain the consequences of losing it: it generates the osmotic pressure that keeps fluid inside blood vessels, so a low albumin lets fluid leak into tissues and cause swelling; and it binds and transports calcium, bilirubin, fatty acids, thyroid and steroid hormones and many medications, so a low albumin changes how those are measured and how drugs behave.

The test measures the albumin concentration in grams per deciliter. A low result can mean less is being made, more is being lost, or the same amount is diluted in more fluid, and the rest of the panel usually says which. Albumin also falls quickly during any significant illness, because the liver diverts its output to inflammation proteins; that makes it a poor stand-alone measure of nutrition, despite its history as one.

Albumin holds fluid inside blood vessels, so when it falls substantially fluid leaks into the tissues:

Low albumin is a marker of something else rather than a disease itself — liver disease (the liver makes it), kidney disease that leaks protein into the urine, malnutrition or malabsorption, severe inflammation or infection, heart failure, or simply being acutely ill in hospital — so the work-up is a search for the cause.

A high albumin is almost always dehydration concentrating the blood and settles with fluids. Albumin also binds about half of blood calcium, so a low albumin lowers total calcium without changing the active fraction.

Albumin is on every comprehensive metabolic panel and hepatic panel and so is checked routinely. It is ordered deliberately in known or suspected liver disease, where it is one of the measures of how well the liver is working; in kidney disease and any swelling of the legs or around the eyes, where protein loss in the urine is the question; in inflammatory bowel disease, celiac disease and other conditions that lose protein through the gut; in malnutrition and eating disorders as one of several markers; in heart failure and fluid overload; and to correct a calcium result, since about half of blood calcium rides on albumin.

Albumin comes with the comprehensive metabolic panel and the hepatic function panel, from your doctor or online through TestWell for a draw at a Quest or Labcorp patient service center, with a licensed physician reviewing the order and results in your portal within one to three business days. Ordering the comprehensive panel gives calcium, kidney function and liver enzymes alongside, which is how a low albumin is interpreted; a urine albumin-to-creatinine ratio in the same visit checks the kidney directly.

Fasting is required for the glucose on a metabolic panel. Drink normally: dehydration raises albumin through concentration, and lying down for a long time before the draw lowers it slightly as fluid shifts. Tell the ordering physician about recent illness or surgery, alcohol use, pregnancy and medications; a level drawn during an acute illness reflects the illness and is rechecked once recovered.

Most laboratories report a normal adult albumin of about 3.5 to 5.0 grams per deciliter; some ranges begin at 3.4 or 3.8 and end at 4.8 or 5.4, and the range on your report applies. Levels are similar in men and women, decline slowly with age, and fall by roughly half a gram in pregnancy through normal plasma expansion.

Hypoalbuminemia is generally defined as a value below about 3.5; values below 3.0 usually come with visible swelling, and values below 2.5 indicate serious disease. Albumin is read with total protein, since a low albumin with a high total protein points to an excess of other proteins, as in myeloma or chronic inflammation, while a low albumin with a low total protein points to loss or dilution; with the liver enzymes and bilirubin; with kidney function and urine protein; and with hs-CRP, since inflammation is the most common reason albumin falls.

The most common cause of a low albumin, particularly in anyone who is or has recently been unwell, is inflammation: albumin is a negative acute-phase protein, meaning the liver makes less of it during infection, injury, surgery and inflammatory disease, and the level recovers over weeks afterward. Chronic liver disease, especially cirrhosis, lowers production directly and is the cause to consider when the liver enzymes, bilirubin or clotting time are also abnormal. Loss through the kidneys, nephrotic syndrome, produces a low albumin with heavy protein in the urine and marked swelling; loss through the gut occurs in inflammatory bowel disease, celiac disease and protein-losing enteropathy.

Dilution lowers albumin without any deficit: heart failure, intravenous fluids, pregnancy and the fluid overload of kidney disease. Malnutrition and malabsorption lower it slowly and are usually accompanied by weight loss and other deficiencies; an isolated low albumin in a well-nourished person is almost never a nutrition problem. Burns and severe skin disease lose albumin through the skin. Symptoms are those of fluid shift, swelling of the ankles, legs and around the eyes, fluid in the abdomen, and breathlessness from fluid in the lungs, together with those of the underlying disease.

Because albumin carries calcium, a low albumin makes the total calcium read low even when the active calcium is normal; laboratories and clinicians correct for this, and ionized calcium measures the active fraction directly.

A high albumin almost always means the blood is concentrated: dehydration from illness, heat, exercise or inadequate fluid intake, or a prolonged tourniquet during the draw, which concentrates proteins locally. No disease makes the liver overproduce albumin. A mildly high value in someone who has not been drinking normally needs only a repeat after rehydration; a high albumin with a high sodium, BUN or hematocrit confirms dehydration.

For a low albumin: hs-CRP for inflammation; a hepatic panel with bilirubin and PT/INR for the liver; creatinine with eGFR and a urine albumin-to-creatinine ratio for the kidney; total protein and, if it is high, protein electrophoresis; and a review of gut symptoms, weight and diet. If the level was drawn during an illness, a repeat after four to six weeks of recovery often resolves the question on its own. For a high albumin: repeat well hydrated.