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Kidney Health

Urea

Urea is a waste product your body makes when it breaks down protein, and your kidneys clear it from your blood — so a urea test is one way to check how well they are filtering. It is easily swayed by everyday things like how much protein you eat and how hydrated you are, so a result outside the range is usually read alongside other kidney tests.

Standard Care
CategoryKidney Health
Reference rangeSee your report
Evidence✓Standard Care
Last updated3 July 2026
On this page

What is urea?

When your body uses protein, it produces ammonia and nitrogen, which are toxic in any amount. Your liver packages these into urea — a far less harmful waste product — and releases it into your blood. Your kidneys then filter the urea out and remove it in your urine. Measuring the urea left in your blood gives a rough sense of how well your kidneys are clearing waste, and is also influenced by your protein intake and how hydrated you are.

Why is it tested?

Urea is measured as part of a kidney function check, usually together with creatinine, electrolytes and eGFR. Looking at them together gives your GP a fuller read on how well your kidneys are filtering — a high urea alongside a high creatinine, for instance, can point to reduced kidney function or simply to dehydration. On its own, urea is easily swayed by everyday factors such as diet and fluids, so it adds useful context rather than being the deciding number.

Reference range (Australia)

No single harmonised Australian reference interval — use the range printed on your report mmol/L

Urea levels shift with hydration, protein intake and muscle, so laboratories set their own reference intervals rather than sharing one national figure. The range printed on your own report is the one to read your result against, and your GP usually looks at it alongside your creatinine and eGFR.

Reference intervals vary between laboratories. Always use the range printed on your own report.

What your result means

If your level is low

A lower-than-usual urea is uncommon and rarely a concern on its own. It can go alongside a low-protein diet, significant liver disease (since the liver is where urea is made), or pregnancy. Your GP interprets it in the context of your wider health rather than in isolation.

If your level is in range

A urea within the range on your report suggests your kidneys are clearing this waste as expected, and that your protein intake and hydration are reasonably balanced.

If your level is high

A higher-than-usual urea can reflect reduced kidney filtering, but it very often has a simpler explanation. Being dehydrated or eating a lot of protein can both raise it, since urea is the waste left over when your body breaks protein down. Your GP will look at it together with your creatinine and eGFR, and ask about your fluids and diet, to work out whether it points to your kidneys or to something temporary.

What can affect your result

Urea moves with several everyday factors, which is part of why it is read alongside other kidney markers rather than alone. Diet and hydration are the big ones. Because urea is the waste left over when your body breaks down protein, a high-protein diet tends to raise it, while a low-protein diet lowers it. Dehydration concentrates urea in the blood; drinking enough brings it back down. Your liver matters too: since the liver is where urea is made, significant liver disease can lower it. Some medicines, recent bleeding in the gut, and your muscle mass can also nudge the number. Your GP takes these into account when reading your result.

When to act

If your urea is outside the range on your report, it is best read together with the rest of your kidney results rather than on its own. Your GP will usually look at your creatinine and eGFR, and ask about your fluids, diet and medicines, to understand what is behind it. A high urea that settles after rehydrating, or that sits on its own with normal creatinine and eGFR, is often reassuring; a pattern of change across your kidney markers is what prompts a closer look. This page is general information and is not a substitute for advice from your GP.

Frequently asked questions

Reference ranges for urea differ a little between laboratories, because urea levels shift with how much protein you eat and how hydrated you are. The range printed on your own report is the one to read your result against, and your GP usually looks at it alongside your creatinine and eGFR.

Urea is a waste product formed when your body breaks down protein. As protein is used, it releases ammonia and nitrogen, which are toxic; your liver converts these into urea, which is much less harmful, and your kidneys then filter the urea out of your blood and remove it in your urine.

No. A high urea can reflect reduced kidney function, but it is just as often explained by dehydration or a high-protein diet. Because urea is swayed by these everyday factors, your GP reads it together with your creatinine and eGFR, which give a more reliable picture of how your kidneys are working.

Yes. Urea is the waste left over when your body breaks protein down, so a diet very high in protein can raise it. In someone with healthy kidneys this is usually harmless, but it is one reason your GP interprets urea alongside your other kidney results rather than on its own.

Urea and creatinine are both waste products your kidneys filter, but they behave differently: urea is more affected by diet and hydration, which is why your GP reads it together with creatinine and your eGFR rather than on its own. A high urea alongside a high creatinine can point to reduced kidney function or dehydration, so reading them together gives a fuller picture than either number alone.

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