Urea is a waste product which is produced by the liver when proteins are metabolised into amino acids and the amino acids are broken down. The liver produces urea from the ammonia produced by the deamination (removal of an amino group through the addition of a hydrogen atom) of amino acids.
When amino acids are broken down, the liver produces nitrogen in the form of ammonia. The nitrogen joins with other chemicals in the liver to produce urea. The urea then leaves the liver and travels via the bloodstream to the kidneys. The kidneys filter the blood removing waste products including urea and excretes them from the body in the urine. When our kidneys are healthy and functioning well, they will remove approximately 90% of the urea produced by the body. Therefore, testing the amount of urea in your blood can give a good indication of how well the kidneys are functioning.
High levels of urea in the blood can be indicative of a reduced kidney function. Symptoms of kidney disease can vary but may include:
However, urea is not an exclusive marker for kidney disease, but also for other conditions including congesting heart failure, stress and dehydration. High levels can also be seen following high protein intake via the diet or via a bleed.
Low levels of urea are not as common and are usually not a cause for concern. Women who are pregnant can have low urea levels as can those who are malnourished or who have liver disease.
Although chronic kidney disease is associated with decreased kidney function, it is possible to see some improvement. If your levels are mildly low, it may be possible to see improvements by making some changes to your lifestyle. You should also ensure you keep yourself adequately hydrated particularly when exercising and during hot weather.
Eating a healthy, balanced diet could also contribute to an improvement in eGFR (estimated glomerular filtration rate) values. The eGFR measures how well the kidneys are filtering the blood of waste products. As urea is a waste product, the better the kidneys are filtering the more waste products they will remove. A study by Miyatake et al., (2011) found that eGFR could be improved through lifestyle changes including a reduction in abdominal circumference. A greater waist to hip ratio can mean you are at greater risk of decreased filtration. You should keep your salt intake low – less than 6g per day.
The Mediterranean diet is associated with a reduced risk of chronic kidney disease as well as other medical conditions. The Mediterranean diet is classified by a high intake of vegetables, fruit, legumes, nuts, cereals and olive oil, a low intake of dairy products, saturated fats, meat and poultry. Instead, the diet encourages a moderate intake of fish and has been linked to a reduced risk of mortality.
Exercise is an important factor in a healthy lifestyle. In general, most people should aim to carry out around 150 minutes of aerobic exercise every week. Exercises may include walking, jogging, swimming, cycling, team sports and tennis. However, you should spread the amount of exercise over a few days.
A study has shown that patients who have cardiovascular disease and chronic kidney disease could improve their renal function with exercise therapy.
 National Center for Biotechnology Information. (2018). PubChem Compound Database; CID=1176, https://pubchem.ncbi.nlm.nih.gov/compound/1176.
 Lab Tests Online UK. (2016). Urea Test. Available at: https://labtestsonline.org.uk/tests/urea-test
 Weis, L., Metzger, M and Haymann, J, P et al., (2013). Renal Function Can Improve at Any Stage of Chronic Kidney Disease. PLOS One.
 Miyatake, N., Shikata, K., Makino, H and Numata, T. (2011). Decreasing Abdominal Circumference is Associated with Improving Estimated Glomerular Filtration Rate (eGFR) with Lifestyle Modification in Japanese Men: A Pilot Study. Acta Medica Okayama: 65(6), pp 363-367.
 Huang, X., Jiménez-Moleón and Lindholm, B et al., (2013). Mediterranean Diet, Kidney Function, and Mortality in Men with CKD. Clinical Journal of the American Society of Nephrology: 13(5).
 Toyama, K., Sugiyama, S and Oka, H et al., (2010). Exercise Therapy Correlates with Improving Renal Function Through Modifying Lipid Metabolism in Patients with Cardiovascular Disease and Chronic Kidney Disease. Journal of Cardiology: 56, pp 142-146.