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What is Protein in Urine?

The kidneys remove wastes and excess water and salts from the blood. Kidneys receive blood through the renal arteries. The blood flows into parts of the kidney called nephrons. Each nephron is made of a glomerulus and a tubule. Each kidney contains thousands of nephrons.

The glomeruli filter the blood, removing waste products from the blood. They also prevent some substances, such as protein, from being taken out of the blood. If the glomeruli are damaged, protein from the blood leaks into the urine.

Normally, you should have less than 150 milligrams of protein in the urine per day. Having more than 150 milligrams per day is called proteinuria. 




Most people with proteinuria have no signs or symptoms. However, some patients have swelling in the face, legs, or both.

The urine may also appear bubbly or soapy.


Proteinuria is diagnosed by analyzing the urine called a urinalysis. 

If two or more urinalyses show protein in the urine, the next step is to determine how much protein is in the urine.

Blood testing — You may be asked to have blood tests to see how well your kidneys are working (called kidney function testing). This includes measurement of BUN (blood urea nitrogen), creatinine, and then calculating how well the kidneys work with a formula called glomerular filtration rate.

Renal biopsy — After your initial evaluation and review of additional testing, the nephrologist at Kidney Care Specialists of Michigan might recommend a test called a renal biopsy. During a biopsy, a doctor takes a small piece of one kidney and then looks at the tissue under the microscope. Most people with proteinuria will not need a kidney biopsy.


A nephrologist is called when your doctor sees a change on your blood test called a creatinine. When the creatinine goes up, the kidney is not getting rid of creatinine and that is how we know there is a kidney problem.

We treat the underlying cause of kidney problem and this will usually stop many of the symptoms, so our patients typically don’t experience any distress while they are having the problem treated.

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