Swollen legs and face: which tests reveal the cause

In shortFor edema, test: creatinine and urea — kidney function; albumin and total protein — low protein lets water escape vessels into tissue; TSH — hypothyroidism gives dense facial swelling; glucose — diabetes damages kidneys; a urinalysis — protein in urine as a trace of kidney loss. Morning facial swelling suggests kidneys, evening leg swelling suggests veins and heart: localization guides the doctor's route.

Where the extra water comes from

Edema is water that has left the vessels for the tissues. Two forces hold it inside vessels: plasma proteins, above all albumin, and kidneys that excrete the excess. The heart as a pump and the thyroid govern the process from above.

So the laboratory search for edema is built around four lines: creatinine and urea (kidneys), albumin and total protein (water retention), TSH (thyroid), glucose (diabetic kidney disease). Plus a urinalysis — cheap and very informative.

Kidneys: creatinine, urea, and urinalysis

Kidney edema is recognizable: face and eyelids in the morning, less by evening. Kidneys losing protein or poorly excreting water — creatinine and urea show filtration, while a urinalysis shows protein loss and traces of inflammation.

Diabetes accelerates kidney trouble, so glucose is mandatory with edema, and people with diabetes get urine albumin added — the earliest marker of kidney problems, visible years before creatinine rises.

Protein and thyroid

Albumin and total protein fall with liver disease, kidney losses, and prolonged undernutrition — and water literally leaks out of the vascular bed. Low albumin with edema is a finding that reroutes the entire workup.

Hypothyroidism gives a special, dense edema: face, eyelids, tongue, a hoarse voice, and no pit from a finger press. If swelling travels with chilliness, weight gain, and sluggishness — TSH first.

When the cause is not in the lab

Evening swelling of both legs after a day on your feet is more often venous — here a vein specialist and duplex ultrasound are needed, not a laboratory. Edema with shortness of breath and a racing heart calls for an ECG and a cardiologist: a pump cannot be checked with a blood test.

A separate warning: one-sided leg swelling with pain is not "wait until Monday" but an urgent exclusion of thrombosis. A doctor is needed today; tests can wait.

The basic set for edema

Creatinine and urea — kidney filtration
Albumin and total protein — holding water in the vessels
Urinalysis — protein loss and inflammation
TSH — hypothyroidism gives dense facial swelling
Glucose — diabetes as a cause of kidney disease

Markers covered in this article

Creatinine BUN (blood urea nitrogen)Albumin Total protein TSH (thyrotropin)Blood glucose Sodium Nechiporenko urine test

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Frequently asked questions

Swelling only in the evening and only the legs — kidneys?

Probably not: kidney edema favors mornings and the face. Symmetric evening leg swelling after a day on your feet is classic venous insufficiency; if breathlessness joined in, have the heart checked.

Can I take a diuretic for the swelling?

Not without a diagnosis: diuretics harm with low protein or thrombosis, and the edema returns stronger. Tests and a doctor first, then — if needed — medication with potassium monitoring.

One leg swelled up — what to do?

One-sided swelling with pain and tightness is a reason to seek help the same day: deep vein thrombosis must be excluded. Do not massage, do not warm, do not wait for tomorrow.

Sources

Creatinine Test: MedlinePlus Medical Test — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.
Creatinine blood test: MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.
Albumin Blood Test: MedlinePlus Medical Test — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.
Albumin blood (serum) test: MedlinePlus Medical Encyclopedia — MedlinePlus, National Library of Medicine. Accessed: August 29, 2026.