What is albumin?
Albumin is a protein produced exclusively by the liver and accounts for about 60% of total plasma protein. It performs several vital functions: maintaining oncotic pressure (keeping fluid inside blood vessels), transporting hormones, drugs, fatty acids, bilirubin and ions through the blood, and acting as an antioxidant and buffer. Albumin has a half-life of about 20 days, making it a useful marker of nutritional and liver status over weeks — not days. It is measured as part of a liver function test (LFT) panel and in kidney (nephrotic syndrome) workup.
Albumin normal range
| Category | Range (g/dL or g/L) | Interpretation |
|---|---|---|
| Normal (adults) | 3.5 – 5.0 g/dL (35 – 50 g/L) | Normal |
| Mildly low | 3.0 – 3.4 g/dL | Mild hypoalbuminaemia |
| Moderately low | 2.5 – 2.9 g/dL | Moderate |
| Severely low | < 2.5 g/dL | Severe — clinically significant |
What does LOW albumin mean?
Low Albumin — Hypoalbuminaemia
Low albumin is called hypoalbuminaemia. It almost always indicates one or more of the following: (1) Liver disease (cirrhosis, hepatitis) — the liver cannot make enough albumin; albumin is a sensitive indicator of liver synthetic function, and a falling albumin in liver disease indicates deterioration. (2) Nephrotic syndrome — the kidneys are losing protein into the urine, causing low blood albumin and oedema. (3) Malnutrition or malabsorption — insufficient amino acid intake or absorption to synthesise albumin. (4) Severe acute illness, sepsis or major burns — albumin moves out of the bloodstream into inflamed tissues (capillary leak) and production falls. (5) Protein-losing enteropathy — GI conditions (Crohn disease, lymphoma) causing protein loss through the gut.
Why does low albumin cause swelling?
Albumin is the main protein maintaining oncotic pressure (the force that keeps fluid inside blood vessels). When albumin falls below about 2.5 g/dL, oncotic pressure drops and fluid leaks from the bloodstream into surrounding tissues, causing oedema (swelling in the legs, ankles, abdomen and around the eyes). This is pitting oedema and is one of the key physical findings in hypoalbuminaemia from any cause.
High albumin — what it means
High albumin (hyperalbuminaemia) is almost always due to dehydration, which concentrates the blood. It is treated by ensuring adequate fluid intake.
Questions to ask your doctor
- Is my low albumin from liver, kidney or nutritional causes?
- Should I have a urine protein test to check for nephrotic syndrome?
- Does this affect drug dosing (some drugs are albumin-bound)?
- Am I getting adequate protein in my diet?
- What is my liver's overall synthetic function?