The most important thing here is context. For a biohacker practicing intermittent fasting, urine ketones are a useful metric to track progress into the state of ketosis. For someone with uncontrolled diabetes, early detection of urine ketones can be a lifesaver….
Monitoring ketone levels in urine is especially important for people with diabetes when they are ill, stressed, or have persistently high blood glucose levels. A positive test result for urine ketones in people with diabetes may be a warning sign for ketoacidosis – a serious complication of diabetes (primarily type 1) associated with extremely high levels of ketones in the blood. If left untreated, diabetic ketoacidosis can lead to coma and death.
Ketones can sometimes be found in the urine of non-diabetics as well, though usually at considerably lower levels. Tracking urine ketones with test strips can be useful for people who are fasting, following a ketogenic diet, or supplementing their diet with exogenous ketones. If you are just starting the ketogenic diet, limiting carbohydrate foods and increasing fat intake enough to promote ketone production can be very challenging. In addition, the amount of carbohydrate restriction needed to get into ketosis varies from person to person. Exercise, fasting, and the amount of food you eat can affect ketone levels as well.
Testing urine for ketosis provides quick and easy feedback on whether the ketogenic diet is working. If weight loss is your goal, measuring ketones in urine lets you know if you are making ketones and burning body fat. Athletes and biohackers following a ketogenic diet or supplementing their normal diet with exogenous ketones like HVMN Ketone can also utilize the information from urine ketone testing. Urine test strips provide a quick and easy way to assess whether the user is staying in ketosis in pursuit of optimizing health and performance.
On the downside, urine test strips are far less accurate than blood meters because they do not give you an actual value. Whilst different color intensities roughly correspond to increasing levels of urine ketones, this is what is called a “non-quantitative” measurement (meaning the reading is not a numerical value). In addition, when you’re following a ketogenic diet, urine tests become less reliable as you become better adapted to using ketones and fatty acids as metabolic fuels. As you transition from being a “sugar-burner” to a “fat-burner,” your body burns more ketones and also wastes less in the urine.
Basics of Ketone Metabolism
Let’s recap the basics of ketone metabolism: the two predominant ketone bodies in human metabolism – acetoacetate (ACAC) and beta-hydroxybutyric acid (BHB) – are made in the liver from fatty acids when glucose is not available. They are then transported in blood to other body tissues to be used as an energy source. Acetone, the third and least abundant ketone, is spontaneously formed from the breakdown of acetoacetate. It is found mostly in your breath, and its contribution as an energy source is negligible. While there are always some ketones present in the blood, their levels naturally increase (ketosis) in response to fasting, prolonged or strenuous exercise, and a low-carbohydrate ketogenic diet.1
Like glucose, ketones are important metabolic fuels that are reabsorbed through the kidneys as the blood is filtered. When blood passes through the kidneys, all small molecules like glucose and ketones end up in the urine, and so must be taken back up. Reabsorption of ketones prevents energy wastage and is especially important during extended fasts. It makes sense that the body doesn’t want to flush good energy down the drain! Ketones appear to be completely reabsorbed from the urine at low blood levels, e.g. after an overnight fast. When the level of ketones in the blood exceeds the reabsorption capacity of the kidneys, the excess ketones spill over into the urine. At this point and beyond, the amount of ketones excreted in the urine increases in direct proportion to the level of ketones in the blood.1 Daily self-testing for ketones in urine is a common approach that can let you know whether you are in ketosis.2
Nutritional (or “physiological”) ketosis is often confused with diabetic ketoacidosis. However, while both conditions involve elevated blood ketones, they are very different. Nutritional ketosis is a benign metabolic state that even occurs naturally in newborn infants and pregnant women. It’s the state people are aiming for when they follow the ketogenic diet or do intermittent fasting. By contrast, diabetic ketoacidosis is a medical emergency.1
Save in nutritional ketosis, ketones in the blood are mildly to moderately elevated. This occurs when other energy sources are limited (fasting, carbohydrate restriction) or depleted (prolonged or strenuous exercise). Circulating levels of beta-hydroxybutyric acid rise above 0.5 mmol/L and can reach maximum levels of 7 to 8 mmol/L.3 In healthy people with a normal pancreas, these ketone levels do not go higher because they are regulated and controlled by the hormones insulin and glucagon, plus ketones themselves slow down fat release to limit their own production.4
Nutritional ketosis triggered by a ketogenic diet is associated with a variety of health benefits, including weight loss, improved blood glucose control, lower triglycerides, higher HDL levels, and improved mental clarity and energy. It has been used as a therapy for epilepsy since the 1920s, and increasing evidence suggests it has therapeutic potential in a variety of chronic diseases, including diabetes, neurological diseases, cancer, and cardiovascular disease.3 Nutritional ketosis may also improve endurance performance and recovery from exercise.5,6
From an evolutionary perspective, ketosis enabled us to survive periods of prolonged starvation. In starvation, the ketone beta-hydroxybutyric acid takes the place of glucose as the primary fuel for the brain, providing as much as 70% of the brain’s energy needs. In fact, beta-hydroxybutyric acid has been described as a “superfuel” because it more efficiently generates cellular energy than glucose or fatty acids.7,8
Diabetic ketoacidosis (DKA) is a life-threatening complication of diabetes mellitus that requires emergency treatment. Early symptoms of DKA include symptoms of high blood sugar – dry mouth, excessive thirst, and frequent urination. Then other symptoms such as fatigue, nausea, vomiting, and abdominal pain appear. Patients may also experience heart racing and rapid breathing.9
Diabetic ketoacidosis occurs when there is a shortage of insulin in the body, leading to uncontrolled diabetes. Without sufficient insulin to shuttle glucose into muscle cells and other tissues to be used for energy, blood glucose builds up to very high levels. High blood sugar levels cause a significant loss of fluids and electrolytes. Meanwhile, the liver begins to burn fatty acids as an alternative energy source, resulting in the accumulation of extremely high levels of ketones in the blood.9 These ketone levels (> 20 mmol/L) can exceed normal fasting levels more than 200 to 300 times!1 Since ketones are mildly acidic, this deluge of ketones causes the blood to become excessively acidic (metabolic acidosis), increasing the risk of coma and death if not timely treated.
So now we know why you might test for urine ketones, let’s dive into how to do it…
Over-the-counter ketone strips can be used for home testing urine ketones. Urine testing is specific for the ketone acetoacetate. It does not detect beta-hydroxybutyric acid, which is measured via blood testing. To perform the test, pass the test end of a ketone strip through a stream of urine, or dip it into a fresh urine sample and remove it immediately. Wait exactly 15 seconds, and match the test end of the strip to the ketone color chart on the container. Ignore color changes that occur after 15 seconds. The color blocks on the chart indicate a negative result or varying degrees of positive – trace, moderate, or large. Dark purple signifies the highest level of ketones (acetoacetate) present in your urine. Studies have suggested that urine testing for ketosis is most reliable when performed in the early morning and late evening after dinner.2,10
While ketones can also be tracked in the blood and breath, urine is the most common method. Measuring ketones in urine has its advantages and disadvantages that you should consider when deciding how to test:
You may have heard that urine ketone results change if you stay on a keto diet for several weeks. What’s going on there?
During prolonged starvation, the body undergoes a profound shift from running mostly on glucose to reliance on fat-based fuel sources: ketones and fatty acids. The ketogenic diet mimics this “keto-adapted” metabolism of starvation.13 In the first few days on a ketogenic diet, you begin producing ketones, some of which are excreted in the urine. Color changes on your urine ketone strips show that you are in ketosis (if not, you may need to make some adjustments in order to get into ketosis, e.g. further reduce intake of carbohydrates, increase fat intake, exercise more, fast, or take exogenous ketones).
As you continue on the diet, you become more adapted or accustomed to making and burning ketones. More ketones are reabsorbed and used for energy, and fewer ketones overflow into the urine.14 After a few weeks to a month, as your ketone levels rise, evidence suggests your muscles shift to burning fatty acids directly while burning fewer ketones. In this way, ketones are spared for use by other tissues, particularly the brain (which does not burn fatty acids for fuel).15,16
Once you are keto-adapted (or fat-adapted), you may get a negative test result on your urine ketone strips, even though blood ketone levels may indicate that you are in ketosis. Over time, then, urine testing is less accurate than blood testing. How frustrating!
Measuring ketones in urine has its place in both a healthcare and health optimization setting. Crucially, it allows for early detection and treatment of uncontrolled diabetes and mitigates the risk of developing ketoacidosis.
In contrast, nutritional ketosis is the body’s physiological response to a shortage of carbohydrate fuel resulting from a ketogenic diet, fasting, or prolonged exercise. Tracking urine ketones with test strips offers you a quick and easy way to know if you are in ketosis. They can be very useful when you are just getting started on a ketogenic diet. Urine ketone testing can serve as a rough guide to help you know whether you are on the right track.
However, as you continue on the diet and become keto-adapted, you excrete fewer ketones. At this stage, urine test strips are less reliable. In addition, urine testing does not accurately quantify your level of ketosis. For instance, you may wish to reach a certain level of ketosis associated with a specific benefit, e.g. exercise recovery. In this case, blood testing is more appropriate since it measures the concentration of beta-hydroxybutyric acid directly in your circulation. Finally, urine ketones do not accurately detect the rapid onset of ketosis triggered by exogenous ketones such as HVMN Ketone.
Overall, urine testing for ketones is clearly convenient and useful for many people. However, those on a long-term ketogenic diet or those using exogenous ketones should beware, as urine strips are unfortunately less accurate than blood testing.
Paoli, A., Bianco, A., Grimaldi, K.A., Lodi, A., and Bosco, G. (2013). Long term successful weight loss with a combination biphasic ketogenic Mediterranean diet and Mediterranean diet maintenance protocol. Nutrients 5, 5205-17.
Manninen AH. Metabolic Effects of the Very-Low-Carbohydrate Diets: Misunderstood “Villains” of Human Metabolism. Journal of the International Society of Sports Nutrition. 2004;1(2):7-11. doi:10.1186/1550-2783-1-2-7.
Sharman MJ, Kraemer WJ, Love DM, Avery NG, Gomez AL, Scheett TP, Volek JS. A ketogenic diet favorably affects serum biomarkers for cardiovascular disease in normal-weight men. The Journal of nutrition. Jul 2002;132(7):1879-1885.
Taboulet P, Haas L, Porcher R, Manamani J, Fontaine JP, Feugeas JP, Gautier JF. Urinary acetoacetate or capillary beta-hydroxybutyrate for the diagnosis of ketoacidosis in the Emergency Department setting. European journal of emergency medicine: official journal of the European Society for Emergency Medicine. Oct 2004;11(5):251-258.
Kemper, M.F., Srivastava, S., Todd King, M., Clarke, K., Veech, R.L., and Pawlosky, R.J. (2015). An Ester of beta-Hydroxybutyrate Regulates Cholesterol Biosynthesis in Rats and a Cholesterol Biomarker in Humans. Lipids 50, 1185-1193.
The Art and Science of Low Carbohydrate Living: An Expert Guide to Making the Life-saving Benefits of Carbohydrate Restriction Sustainable and Enjoyable. Jeff Volek, Phd Stephen D. Phinney MD, Rd Jeff S. Volek Phd, Stephen D. Phinney. Beyond Obesity, 2011.
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