Creatinine is a waste product produced from the metabolism of creatine. Creatine is converted from phosphocreatine when muscles contract. The production of creatinine varies very little from day to day because it is a product of muscle activity and the muscle mass of an individual remains almost constant. Creatine and creatinine are filtered by the kidney, creatine is reabsorbed but creatinine is excreted in the urine.
A creatinine blood test measures how much creatinine there is in your blood, almost all the creatinine in the body is excreted in the urine via the kidneys. Therefore, blood levels of creatinine are a good indicator of how well your kidneys are working.
There are differences between how much creatinine is excreted by men, women and children because the quantity produced is dependent upon gender, age and size of the individual. Increased blood levels of creatinine usually indicate the presence of disease which affects the function of the kidneys, whereas low levels are not usually any cause for concern.
Creatinine is a waste product, produced by the muscles from the breakdown of creatine. Creatine is an important part of the energy cycle used to contract muscles.
Because creatinine is a measure of how well the kidneys are functioning, if the kidneys are not working properly some of the symptoms can have a negative impact on your health and wellbeing. For example, a high creatinine level may be a result of kidney stones. Although small stones can pass through when we urinate and may not cause any symptoms, large stones can cause pain as well as other physical symptoms.
Dehydration has been shown to be a risk factor for kidney disease. Dehydration can affect both mental status and physical health, but this is reversible through rehydration.
Intense exercise and injury may raise creatinine levels because of both results in increased muscle breakdown. Plus, injury can mean a longer recovery period and may interfere with training programmes.
If you are worried about your creatinine level or just want to check where you fall on the range, you can test your level with a simple at-home blood test.
There are several factors which can cause changes in creatinine levels. Elevated levels can be caused by:
Although lower levels of creatinine are uncommon and not usually anything to worry about, they may be due to:
Increased levels of creatinine in the blood usually indicate reduced kidney function. Symptoms of kidney disease can vary between individuals but can include:
Sometimes, high levels of creatinine may indicate muscle injury. If your creatinine levels have increased because of injury or you have participated in intense exercise they should return to normal after a recovery period.
Low creatinine levels are uncommon but are not usually any cause for concern. Individuals with low muscle mass or females who are pregnant may have low creatinine levels.
Kidney function can be maintained and even improved by making some changes o your lifestyle. Research has shown reducing abdominal circumference in people with metabolic syndrome can improve estimated glomerular filtration rate (eGFR). A greater waist to hip ratio can increase the risk of decreased filtration.
Diet is helpful in improving eGFR, particularly the Mediterranean diet as this reduces the risk of developing chronic kidney disease as well as other medical conditions.  The diet has been linked to a lower risk of mortality and is characterised by a high intake of fruit, vegetables, legumes, nuts, cereals, and olive oil as well as a moderate intake of fish. The diet is low in meat, saturated fat and poultry.
Exercise is also fundamental in maintaining kidney health. In fact, studies have shown that individuals with cardiovascular disease and chronic kidney disease can improve their kidney function with exercise therapy. 
 NHS South Tees Hospitals NHS Foundation Trust. (2019). Creatinine. Available at: https://www.southtees.nhs.uk/services/pathology/tests/creatinine/
 Lab Tests Online. (2016). Creatinine. Available at: https://labtestsonline.org.uk/tests/creatinine
 NHS. (2019). Kidney Stones. Available at: https://www.nhs.uk/conditions/kidney-stones/symptoms/
 Roncal-Jimenez, C et al. (2015). Mechanisms by Which Dehydration May Lead to Chronic Kidney Disease. Annals of Nutrition and Metabolism: 66 (suppl 3), pp 10-13.
 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.