When is the Best Time to Test Ketones in Urine?

  • Author: Kara
  • Date: September 20, 2023
  • Time to Read: 4 min.
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Testing ketone levels in urine can be a useful way to monitor whether you are in ketosis on a low-carb, ketogenic diet. However, there are some important factors to consider regarding when to test for optimal accuracy.

Overview of Testing Ketones

When following a very low-carb, high-fat ketogenic diet, your body switches from using glucose as its main source of energy to using fat and ketones. This metabolic state is called ketosis.

There are three main types of ketones produced in ketosis:

  • Acetoacetate: First ketone produced from fat breakdown. Not detectable in urine.
  • Beta-hydroxybutyrate (BHB): Main ketone in circulation. Not detectable in urine.
  • Acetone: Generated from acetoacetate. Detectable in urine.

Urine ketone test strips measure acetoacetate that converts to acetone. They provide a rough estimate of ketosis but have some limitations compared to blood tests.

When to Test for Optimal Accuracy

Here are some tips on when you should test your urine to get the most accurate results:

1. Test in the morning

Ideally, you should test your urine for ketones first thing when you wake up in the morning before eating or drinking anything.

This is because food, drink, exercise, medications, and other factors during the day can dilute ketones and influence results.

Testing early morning urine gives a snapshot of your baseline ketone levels after hours of fasting.

2. Hydrate normally the day before

Being well-hydrated can help concentrate ketones in the urine for more accurate testing.

Aim to drink sufficient water and electrolytes the day before testing, but avoid overhydrating right before bed which can dilute urine.

3. Restrict carbs and calories before testing

To get an optimal ketone measurement, restrict your carb intake to 20-30g net carbs or less for 1-3 days before testing.

Also, eat just enough protein to meet your needs and create a calorie deficit to spur ketone production.

This ketogenic approach helps elevate ketones and make them easier to detect.

4. Test after exercise

Engaging in exercise, especially high-intensity exercise, can temporarily raise ketone levels as your body burns more fat for fuel.

Testing urine within 1-2 hours after your workout may show a spike in ketones that provides confirmation of ketosis.

5. Test during weight loss plateaus

Hitting a stall or plateau while trying to lose weight on keto? Testing ketones can help troubleshoot.

If you aren’t showing ketones during a plateau, it may indicate you need to cut back on carbs or calories further to re-enter ketosis and break through the stall.

6. Test if feeling symptoms

Testing when you are experiencing potential keto flu symptoms like fatigue, headaches, nausea, or cramps can help confirm if you are transitioning into ketosis.

If you aren’t showing ketones despite the symptoms, it points to needing further carb reduction.

When Not to Test Ketones

Here are some circumstances where testing ketone levels may be less accurate or useful:

  • Right after eating lots of carbs or calories – this can transiently reduce ketones.
  • Soon after taking certain medications/supplements that influence ketosis like caffeine or MCT oil.
  • During periods of overhydration – this dilutes ketones in urine.
  • If urine is very concentrated and dark – can elevate acetoacetate misleadingly.
  • After intense, prolonged exercise – can briefly raise ketones to untypical levels.
  • During periods of starvation/severe calorie restriction – can increase ketones unrelated to carb restriction.

Optimal Ketone Levels

Here are some general guidelines on optimal ketone levels to look for when testing urine with strips:

  • Trace ketones (5-15 mg/dL acetone): Indicates light nutritional ketosis
  • Small/moderate ketones (40-80 mg/dL): Optimal range for fat burning
  • Large ketones (80-160 mg/dL): Signifies deep ketosis
  • Very large ketones (>160 mg/dL): Risk of ketoacidosis if sustained

Keep in mind urine ketones only provide a rough snapshot and blood ketone meters are more accurate for monitoring your individual optimal range.

Testing Frequency

When first starting keto, testing 1-2 times per day can help confirm you are entering ketosis.

Once adapted to the diet, testing 1-2 times per week is typically sufficient to make sure you are staying in ketosis long-term.

However, increase testing frequency again if making any dietary changes, experiencing plateaus or keto flu symptoms.

Additional Tips for Accuracy

  • Read strips promptly within time specified on package.
  • Check strips haven’t expired – this can affect accuracy.
  • Compare to a color chart each time for best results.
  • Account for factors like hydration status, medicines, exercise when interpreting.
  • Consider tracking with blood ketone meter for more accuracy.

Wrapping Up: When is the Best Time to Test Ketones in Urine?

Testing ketone levels in urine can be a useful feedback tool when starting and sticking with a ketogenic diet long-term. For optimal accuracy, test first morning urine after restricting carbs/calories in a hydrated state. Be aware of factors that can impact results and use screening strips as a general guide alongside clinical monitoring tools.

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