Albumin: the protein that falls when something is wrong

Albumin is made by the liver and makes up about half the protein in plasma. It holds water inside the blood vessels and carries calcium, fatty acids, many drugs and other molecules. It is reported in g/dL in the US or g/L elsewhere (4.0 g/dL is 40 g/L). It is part of a standard comprehensive metabolic panel.

Albumin is a "negative" acute-phase protein: during inflammation the liver makes less of it while making more CRP and fibrinogen. That is why Peptide AI places it in the inflammatory panel.

The ranges

Do not confuse serum albumin with urine albumin. The urine albumin-to-creatinine ratio is a kidney test, covered with eGFR. There is no guideline "optimal" serum albumin for healthy people; claims that higher is always better ignore that a high reading usually means concentrated blood.

What raises and lowers it

• Lowers: acute or chronic inflammation, liver disease such as cirrhosis, kidney disease with protein loss in the urine (nephrotic syndrome), gut conditions that lose or fail to absorb protein, weight-loss surgery, low protein intake and malnutrition, severe burns, pregnancy, and large volumes of intravenous fluid.
• Raises: dehydration, and a tourniquet left on too long or a draw taken after standing for a long time.

Albumin has a half-life of about three weeks, so it responds slowly. A low result usually reflects weeks of a problem rather than days.

What it predicts

In the NHANES I Epidemiologic Follow-up Study (American Heart Journal, 1992), US adults were followed for 9 to 16 years. In white adults aged 45 to 74, albumin of 4.5 g/dL or more was associated with lower death from any cause: relative risk 0.73 in men and 0.71 in women, independent of baseline risk factors. Higher albumin was also linked with less coronary heart disease. Similar findings have come from cohorts of older adults and of people in hospital or on dialysis; a 1998 BMJ review cited a systematic review of cohort studies estimating that each 2.5 g/L lower albumin raised the risk of death by 24 to 56%. The likely explanation is that albumin summarises inflammation, liver function and nutrition, not that albumin itself protects anyone. The same BMJ review pooled 30 randomised trials in 1,419 critically ill patients and found giving albumin did not lower deaths, and the much larger SAFE trial (NEJM, 2004) of 6,997 intensive care patients found albumin and saline gave the same mortality (relative risk 0.99). Raising the number does not buy the outcome.

On GLP-1 drugs and weight loss

The pivotal semaglutide and tirzepatide trials do not report albumin as an outcome. In practice, the reasons it would fall during weight loss are the ones above: very low protein intake for a long period, persistent vomiting, or an unrelated illness. Normal albumin does not prove protein intake is adequate, because the liver protects it until intake is very poor. Muscle and strength are better guides; see the protein intake guide and GLP-1 muscle loss.

How to test

• Usually part of a metabolic panel; fasting is not required but keeps conditions consistent.
• Be hydrated, not overloaded. Dehydration raises it, and lots of fluid lowers it slightly.
• Sit for a few minutes before the draw and keep tourniquet time short.
• Read a low value with hs-CRP, liver enzymes, eGFR and urine albumin to find the cause.

Because albumin changes slowly, a single low-normal result during a short illness says little. A steady downward drift across several draws, especially alongside rising hs-CRP or falling weight that you did not intend, is the pattern worth raising.

Tracking it in Peptide AI

In Peptide AI, albumin sits in the inflammatory panel. The app reads it from a lab PDF or manual entry, scores the panel from 0 to 100 alongside an overall grade, flags values that warrant prompt physician consultation, and plots each result against your dose timeline. Log the draw date, whether you fasted, and anything unusual in the days before, such as illness, a hard session or a dose step, so the next result is compared like with like. Bloodwork tracking shows the series next to the dose log, weight and side effects, and the panels page lists every marker the app groups. More markers are in the bloodwork guides.