Can You Still Be in Ketosis If Urine Strips Say You’re Not?

If you’re following a well-formulated ketogenic diet and suddenly find that your urine test strips no longer show ketones, it’s natural to feel confused or even concerned. Could these strips indicate negative results even though you’re still in ketosis?

The short answer is yes, you can still be in ketosis even if urine strips suggest that you’re not. In fact, for many people who stick with a ketogenic lifestyle over time, a decrease in urinary ketones might be a sign that your body has become more efficient at using ketones for energy.

Let’s take a closer look at why this happens and why urine ketone testing becomes less reliable as you become keto-adapted.

Understanding Ketone Bodies and Urine Testing

When the body begins producing ketones in response to carbohydrate reduction, it generates three main types:

• Acetoacetate is the first ketone body produced in the liver and can be used directly for energy or converted into other ketones.
• Beta-hydroxybutyrate (BHB) is formed from acetoacetate through an enzyme-catalyzed reaction and serves as the main ketone fuel for the brain and body.
• Acetone is spontaneously formed from acetoacetate and is exhaled through the lungs.

Urine ketone test strips are designed to detect acetoacetate. In the early stages of a ketogenic diet, acetoacetate is often excreted in urine in high amounts because the body is still learning how to use it efficiently.(1) This is why ketone strips tend to show strong positive readings early on.

Urine Ketones Often Decline with Keto Adaptation

Over time, the body undergoes several important adaptations that may lead to a natural decrease in urinary acetoacetate:

1. Improved ketone utilization: Once your cells — especially in the brain, muscles, and heart — become more efficient at using ketones for energy, your kidneys start reabsorbing acetoacetate instead of flushing it out in urine.(2)
2. Shift toward BHB: As keto-adaptation continues, your body begins converting more acetoacetate into BHB, which is the primary ketone found in the blood and a more stable energy source.(3) Since urine strips don’t detect BHB, this shift can lead to lower urine readings even as metabolic ketosis deepens.
3. Hydration status: Urine concentration varies based on how much water you drink. Even if you’re in ketosis, high fluid intake can dilute urine and lead to a false negative result on a test strip.(4)

While they’re convenient and affordable, urine ketone strips have limitations. They only detect excess acetoacetate, not how much your body is producing or using. As you become fat-adapted, urinary ketone levels often drop, even when you’re still in ketosis.

This can be discouraging if you’re relying on strips to track progress, but a low or negative result doesn’t mean you’ve failed. It likely just means your body is using ketones more efficiently.

Better Ways to Monitor Ketosis

If you’re looking for a more accurate picture of your ketogenic state beyond the first few weeks, consider these methods:

• Blood Ketone Testing: Blood ketone meters measure BHB and provide a more accurate measurement of your level of ketosis.(5) Drawbacks to this method include the ongoing cost of test strips and the need to prick your finger, which some people find uncomfortable or invasive.
• Breath Ketone Testing: Breath ketone meters or breathalyzers measure breath acetone, which correlates with fat metabolism. Research shows that the amount of acetone in your breath tends to reflect the levels of ketones in your blood, making it a useful way to track whether you’re in ketosis.(6) However, there are some reliability concerns with current technology. Readings can be affected by the device’s accuracy, your breathing technique, and interference from gases like hydrogen, which some devices may mistakenly detect as acetone.(7, 8)
• Clinical Signs: In addition to measuring blood or breath ketones, you can look for signs that your body remains in ketosis. These may include steady energy, reduced hunger, improved mental clarity, and favorable changes in blood sugar or insulin levels.

The Bottom Line

Although they can be helpful in the early stages, urine strips aren’t a reliable way to assess ketosis over time. For a more accurate picture, consider how you feel and use tools like blood or breath testing to confirm your ketone levels.

REFERENCES

1. Ketone bodies: a review of physiology, pathophysiology and application of monitoring to diabetes, Diabetes Metabolism Research and Reviews, 2000
2. Renal conservation of ketone bodies during starvation, Metabolism, 1975
3. Ketone bodies: from enemy to friend and guardian angel , BMC Medicine, 2021
4. Urine dipsticks are not accurate for detecting mild ketosis during a severely energy restricted diet, Obesity Science and Practice, 2020
5. Reliability and diagnostic performance of a new blood ketone and glucose meter in humans, Journal of the International Society of Sports Nutrition, 2021
6. Breath acetone predicts plasma ketone bodies in children with epilepsy on a ketogenic diet, Nutrition, 2006
7. The Ketogenic Diet: Breath Acetone Sensing Technology, Biosensors (Basel), 2021
8. Metal Oxide Gas Sensors to Study Acetone Detection Considering Their Potential in the Diagnosis of Diabetes: A Review, Molecules, 2023

This blog is provided for informational purposes only and should not be considered a replacement for professional medical advice, diagnosis, or treatment. If you have any questions about a health condition or concerns related to your well-being, always consult with your physician or another qualified healthcare professional.