Protein in your urine: what it means and what comes next
Dr. Joan J. Morales Lappot, MD3 min read · Leer en español
In briefProtein in the urine is often the very first sign that the kidneys are under strain, sometimes years before kidney function drops. That makes it one of the most useful tests we have.
Why protein should stay in the blood
The kidney filters are designed to keep large molecules such as albumin in your bloodstream. When those filters are damaged, albumin leaks into the urine. Doctors call this albuminuria or proteinuria.
How it is measured
The best screening test is the urine albumin-to-creatinine ratio (UACR) from a single urine sample. A result under 30 mg/g is normal. Because exercise, fever or infection can raise it temporarily, an abnormal result is usually repeated.
Common causes
- Diabetes
- High blood pressure
- Glomerular diseases such as IgA nephropathy, FSGS or membranous nephropathy
- Lupus and other autoimmune conditions
- Heavy exercise, fever or a urinary infection (temporary)
Why it matters and what helps
Protein in the urine raises the risk of kidney disease getting worse and of heart disease. The good news is that lowering it protects both. Common steps include blood pressure control, less salt, and medicines that lower protein leak, such as ACE inhibitors, ARBs and SGLT2 inhibitors when they fit you. Very high levels, or protein with blood in the urine, may need a kidney biopsy to find the exact cause.