Safety
The Tests a Doctor Runs for Persistent Swelling
Knowing what will be checked makes the appointment shorter and the answer faster. 🩺
Key takeaways
- Urine protein and albumin point at kidney causes.
- BNP or an echocardiogram assesses the heart.
- Thyroid function catches a commonly missed cause.
- D-dimer plus ultrasound is the clot pathway.
Why tests rather than a supplement
Bilateral leg swelling has a short, well-defined differential: heart failure, kidney disease, liver disease, hypothyroidism, medication effects, chronic venous insufficiency and lymphoedema. Most of it is distinguishable with a history, an examination and a handful of blood tests.
That matters because the treatments are completely different. A diuretic helps cardiac oedema and does little for lipoedema. Compression helps venous oedema and is unsafe in significant arterial disease. A botanical supplement addresses none of the serious causes. Getting the label right comes first.
What is usually checked 🧪
- Blood pressure — and a check for raised jugular venous pressure on examination.
- Urine dipstick for protein — a quick, cheap pointer to kidney disease. Frothy urine is the symptom people notice.
- Kidney function — creatinine and eGFR, plus electrolytes.
- Liver function and albumin — low albumin reduces the oncotic pressure holding fluid in the bloodstream. See capillary filtration explained.
- Thyroid function (TSH) — hypothyroidism causes a characteristic non-pitting swelling and is easy to miss.
- Full blood count — anaemia and infection markers.
- BNP or NT-proBNP — a marker of cardiac strain; often followed by an echocardiogram if raised.
- HbA1c — diabetes contributes through several routes.
If a clot is suspected the pathway is different: a D-dimer blood test and a leg ultrasound, usually arranged urgently.
How to make the appointment productive 📝
- Bring your medication list — every prescription, over-the-counter medicine and supplement, with start dates. Drug-induced oedema is common and very fixable; see medicines that cause swelling.
- Bring a timeline. When it started, whether it settles overnight, whether it is one leg or both, and what has changed recently.
- Bring measurements if you have them. Weekly ankle circumference at a fixed point is more useful than “it seems worse”.
- Mention weight changes over days or weeks — rapid gain is a meaningful sign.
- Say if you snore or wake unrefreshed. Sleep apnoea contributes to fluid retention and is frequently undiagnosed.
Once serious causes are excluded and you are left with ordinary venous insufficiency, that is the point at which compression, movement, elevation and — last on the list — a botanical become reasonable to consider. ✅