Why is protein in the urine a sign that something could be wrong with kidneys?

Protein, particularly albumin, shouldn’t be present in urine. So when protein shows up in significant quantities, it implies that the kidneys are leaking protein.

The normal filtering capabilities of the kidney keep albumin and other proteins in the blood. So, when the kidneys are affected by infections or other damage, the filtering system doesn't work as effectively, and proteins like albumin seep out into the urine.

It's important to note that protein in urine, known as proteinuria, isn’t always a cause for concern. Certain conditions, like strenuous exercise, fever, and dehydration, can lead to small amounts of protein in urine. However, persistent or heavy proteinuria is often a sign of underlying kidney problems.