Short answer
An albumin blood test measures a major protein made by the liver. Albumin helps keep fluid inside blood vessels and helps carry hormones, vitamins, enzymes, medicines, and other substances through the bloodstream. Albumin is often included in a comprehensive metabolic panel (CMP) or liver panel.
Low albumin can come from several broad patterns: reduced liver production, kidney protein loss, protein loss or poor absorption through the gut, inflammation or severe illness, malnutrition, burns, pregnancy, or fluid overload. High albumin is often related to dehydration. The result is most useful when interpreted with liver tests, kidney function, urine albumin or protein testing, total protein, globulin, symptoms, and trend.
What albumin does
Albumin is the most abundant protein in the fluid part of blood. MedlinePlus describes two practical jobs: it helps keep fluid from leaking out of blood vessels into tissues, and it helps carry substances through the body. When albumin is low enough, fluid balance can be affected, which is why swelling, abdominal fluid, or shortness of breath may matter in the right clinical setting.
A serum albumin result is different from a urine albumin result. Blood albumin asks how much albumin is circulating in the blood. Urine albumin testing, often reported as a urine albumin-creatinine ratio (uACR), asks whether albumin is leaking into urine and can be a kidney-risk marker.
Why urine albumin is different
Blood albumin and urine albumin are related but not interchangeable. The blood test helps show liver production, fluid balance, inflammation, and protein loss patterns. The urine test, especially uACR, helps show whether the kidneys are leaking albumin. A person can have a blood albumin result that looks normal while urine albumin is abnormal, or the reverse in some illness patterns.
Why low albumin happens
Low albumin is called hypoalbuminemia. It is not one diagnosis. The NCBI Bookshelf hypoalbuminemia review describes a wide differential that includes liver production problems, kidney loss such as nephrotic syndrome, digestive loss or malabsorption, increased breakdown during severe illness, inflammation, and dilution from fluid states.
That is why albumin should not be used as a simple nutrition score. Poor intake can contribute, but inflammation, liver disease, kidney protein loss, fluid overload, pregnancy, infection, and digestive disease can all change the number. The pattern around the albumin often matters more than the albumin alone.
Patterns that change the meaning
| Pattern | What it can suggest | What often helps clarify it |
|---|---|---|
| Low albumin with abnormal liver panel | Reduced liver production or chronic liver disease may be part of the question. | AST, ALT, ALP, GGT, bilirubin, PT/INR, platelets, hepatitis testing, imaging, and trend. |
| Low albumin with urine protein or high uACR | Kidney protein loss may be contributing. | Urinalysis, urine albumin-creatinine ratio, urine protein-creatinine ratio, creatinine, eGFR, swelling, and blood pressure. |
| Low albumin with diarrhea, weight loss, or inflammatory bowel symptoms | Protein loss or poor absorption through the digestive tract may be considered. | Stool testing, celiac testing, inflammatory markers, total protein, globulin, and GI follow-up. |
| Low albumin with swelling, abdominal fluid, or shortness of breath | Fluid shift, liver, kidney, heart, or severe inflammatory causes may need faster review. | Exam, urine protein, kidney function, liver function, imaging, heart evaluation, and medication review. |
| High albumin | Often dehydration or a concentrated blood sample. | Hydration context, BUN/creatinine, sodium, total protein, symptoms, and repeat testing if needed. |
What follow-up may clarify
Follow-up often starts with repeat testing if the result is unexpected, then a pattern check: CMP, total protein, globulin, liver enzymes, bilirubin, kidney function, urinalysis, and urine albumin-creatinine ratio or urine protein-creatinine ratio. Albumin near the edge of the range with an otherwise normal CMP can be very different from clearly low albumin with swelling or abnormal urine protein.
If liver production is the concern, clinicians may look at PT/INR, bilirubin, platelets, hepatitis tests, ultrasound, elastography, or specialist evaluation. If kidney protein loss is the concern, uACR, urine protein, eGFR, blood pressure, diabetes status, and nephrology follow-up may matter. If digestive loss or inflammation is suspected, stool tests, celiac testing, inflammatory markers, or GI evaluation may be considered.
When albumin needs timely care
- Albumin is clearly low, falling, or paired with new swelling in the legs, face, belly, or around the eyes.
- There is shortness of breath, rapid weight gain from fluid, severe abdominal swelling, confusion, fainting, or chest pain.
- Urine is foamy or bloody, urine output changes, creatinine is rising, eGFR is falling, or uACR/urine protein is high.
- Albumin is low with jaundice, abnormal bilirubin, high PT/INR, low platelets, or known liver disease.
- There is persistent diarrhea, significant weight loss, poor intake, fever, severe illness, burns, or concern for a medication reaction.
Questions to ask
- How low or high is my albumin compared with this lab's reference range and my prior results?
- Was albumin measured as part of a CMP, liver panel, kidney workup, or nutrition/inflammation evaluation?
- Are total protein, globulin, AST, ALT, ALP, GGT, bilirubin, PT/INR, platelets, creatinine, eGFR, and electrolytes normal?
- Do I need urine albumin-creatinine ratio, urine protein-creatinine ratio, or urinalysis to check for kidney protein loss?
- Could dehydration, fluid overload, pregnancy, inflammation, infection, digestive disease, burns, medicines, or recent illness affect the result?
- What symptoms or trend would make this urgent?
Frequently asked questions
What does low albumin mean on a blood test?
Low albumin can happen when the liver makes less albumin, the kidneys leak protein into urine, the gut loses or does not absorb protein well, inflammation or severe illness changes protein balance, nutrition is poor, or fluid overload dilutes the blood. The meaning depends on liver tests, kidney tests, urine protein or uACR, symptoms, and trends.
Is albumin a nutrition score?
Not by itself. Albumin can be affected by nutrition, but also by inflammation, liver disease, kidney protein loss, fluid status, pregnancy, burns, infection, and digestive disease. It should not be used as a simple grade of how much protein someone eats.
What does high albumin mean?
High albumin is often related to dehydration or a concentrated blood sample. It is usually interpreted with the rest of the comprehensive metabolic panel, total protein, kidney markers, symptoms, and whether the value normalizes.
Can kidney disease cause low blood albumin?
Yes. Some kidney conditions allow albumin to leak from blood into urine. Urine albumin-creatinine ratio, urine protein testing, creatinine, and eGFR can help show whether kidney protein loss is part of the pattern.
Can liver disease cause low albumin?
Yes. Because albumin is made by the liver, advanced or chronic liver disease can lower albumin. Liver enzyme results, bilirubin, PT/INR, platelets, imaging, symptoms, and trend help distinguish liver production problems from kidney, gut, inflammation, or fluid causes.
What tests may be ordered after low albumin?
Follow-up may include repeat CMP or liver panel, total protein and globulin, urinalysis, urine albumin-creatinine ratio, urine protein-creatinine ratio, creatinine, eGFR, liver enzymes, bilirubin, PT/INR, CBC, inflammatory markers, stool or digestive evaluation, hepatitis testing, imaging, or specialist referral depending on the pattern.
Is blood albumin the same as urine albumin?
No. Blood albumin measures the amount of albumin circulating in the bloodstream, while urine albumin checks whether albumin is leaking into urine. They answer different questions and are interpreted differently.