Such relatively benign conditions as exposure to heat or cold or emotional stress can cause protein in the urine, or proteinuria, according to Mayo Clinic. Fever and intense exercise can cause it as well.
Less benign causes of protein in the urine are diabetes; heart disease, including pericarditis; and high blood pressure, states Mayo Clinic. Hodgkin's lymphoma, leukemia, lupus, malaria and kidney infection can also cause protein in the urine. Kidney disorders, such as glomerulonephritis and Goodpasture's syndrome, can cause it too. Pregnancy can also cause elevated protein levels in the urine, especially a dangerous condition called preeclampsia.
Other causes of proteinuria are sarcoidosis, rheumatoid arthritis and multiple myeloma, says Mayo Clinic. Some people experience protein in the urine when they rise from a prone to an upright position. Sickle cell anemia can also cause protein to appear in the urine. Certain drugs contribute to protein in the urine as does amyloidosis, a condition where proteins accumulate in the bodily organs. Toxins and infections can also cause the disorder, says WebMD.
People who are most at risk for proteinuria are people who are obese or over 65, states WebMD. Those who have or had members of their family with kidney disease and belong to certain ethnic and racial groups are also at risk.