Excess protein in the urine, also known as proteinuria, can have several causes. One of the most common causes is kidney damage or disease, as the kidneys are responsible for filtering waste products from the blood, including excess protein, and excreting them in the urine. In your case, you mention that you have had bad kidneys your whole life and that you have a history of blood and protein in your urine. This suggests that your kidney function may be compromised, which could be the underlying cause of your proteinuria. Other potential causes of proteinuria include: Inflammation or infection of the kidneys Diabetes High blood pressure Certain medications, such as nonsteroidal anti-inflammatory drugs (NSAIDs) Certain autoimmune disorders, such as lupus Certain blood disorders, such as multiple myeloma The pain you are experiencing in your sides and back may also be related to your kidney function, as kidney disease can cause pain and discomfort in the flank area. Low iron levels, or iron deficiency anemia, can also be a complication of kidney disease, as the kidneys play a role in regulating iron levels in the body. It is important to follow up with your healthcare provider regarding your proteinuria and kidney function, as well as any other symptoms you may be experiencing. Your healthcare provider may recommend further testing, such as blood tests or a kidney biopsy, to determine the underlying cause of your proteinuria and develop an appropriate treatment plan.