There's so much confusion when it comes to testing for ketones. People have different opinions on the best method to the best time of day to test for ketones.
For the most accurate ketones measurement, the best time to test for ketones is in the morning while on an empty stomach. The second best time to test for ketones is right before a meal, at least 3 hours after you've had any other food or drink besides water.
In this article, I'm going to cover everything you need to know about determining your level of ketosis, the best method for testing, what to expect, and how often you should be testing.
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Best Time To Test For Ketones
The truth is, the best time to test for ketones on a keto diet will be when it's most convenient for you to check them.
Choosing a convenient time that fits your schedule is essential because you want to continually test at roughly the same time and in the same conditions.Testing in this matter will let you accurately compare one reading to the next, which will help you figure what may be causing variations if any.
This means, if measuring your ketones first thing in the morning is easy for you to repeat daily (or however often you choose), then that's the time to measure your ketone levels FOR YOU.
However, there are factors like sleep and what you've eaten that may alter the result you get. For this reason, I'll go over the different times you may want to test and what may affect your ketone levels at those times.
How Can You Tell If You're In Ketosis?
While there are lists of signs and symptoms you can look out for, such as keto breath or appetite suppression, you can generally measure your level of ketones using three methods.
- Ketone Urine Strips
- Ketone Breath Meter
- Ketone Blood Meter
When it comes to any scientific literature that measures ketones in the body, the gold standard is undoubtedly a ketone blood meter.
However, the other two methods may be just as useful for what most people are trying to accomplish, and I'll explain why and when to test for ketones utilizing each method is.
What's The Best Way To Test For Ketones?
As I briefly mentioned, the gold standard for testing ketones on a ketogenic diet is by using a blood ketone meter.
The majority of the scientific literature suggests that blood ketone testing is more accurate and effective than urine ketone testing. 1
I'll also cover why testing for ketones via urine test may be perfectly fine in the beginning, but may not be ideal as you progress in your diet.
So what exactly is a blood ketone meter? It is similar and sometimes the same device as what people with diabetes use to test their blood glucose levels using glucose strips.
Begin by inserting ketone strips into the meter, followed by pricking your finger to draw out a drop of blood, then place the blood in the tip of the test strip that will measure the level of ketone bodies.
Blood tests will take only a few seconds before your levels are displayed, similar to urine tests.
While all blood ketone meters can also serve as a blood glucose meter, not all blood glucose meters can test for blood ketones.
If you're looking for one that can do both, below are two companies I would recommend purchasing for their accuracy.
- KetoCoach
- Precision Xtra
- Keto Mojo
For now, let's go over the best time to test utilizing the three different methods.
When To Test Blood Ketones
There are two times I would recommend to test blood ketones, and those would be the first thing in the morning or right before dinner.
First thing in the morning
Testing for blood ketones first thing in the morning gives you a good baseline that you can compare over time.
You've fasted for at least a good 8+ hours and haven't had any food or life circumstances that could skew your results compared to testing later in the day.
The cons of testing first thing in the morning is some people may experience what is called the “dawn phenomenon” or “dawn effect.” 2 3
The dawn phenomenon is the term given to describe an increase in blood sugar early in the morning, usually caused by the body's release of certain hormones (cortisol, glucagon, epinephrine). When blood sugar rises, despite the cause, blood ketone levels tend to fall as a result.
To help combat a false reading, it may be best to wait for one to two hours after waking (and before eating) to test your blood ketone levels first thing in the morning.
And that's what I mean by the best time to test is when it's most convenient for you.
If you experience higher blood sugar than normal first thing in the morning and have to wait 1-2 hours to test, this may not be ideal for your lifestyle if you have to continually rush out the door to drop off the kids or go to work at that time.
Before a meal
The next time you should test for blood ketones would be right before dinner.
By dinner time you've had at least one or two meals. Taking a reading at this time almost gives you a better snapshot of how the entirety of your daily activities and diet has affected your ketone levels.
You want to ideally test ~ 3 hours after you've had anything to eat or drink besides water.
Waiting at least 3 hours ensures your body has digested your previous meal, and your ketone readings aren't skewed by the increase in blood glucose you may experience from your last meal.
To be in ketosis, you should have a reading of 0.5 mmol L or higher.
What Time Of Day To Test For Urine Ketones?
Ketone test strips are widely available over the counter at most pharmacies or drug stores without a prescription. Due to its ease of availability and the fact you don't have to prick your finger, many people often resort to urine testing using ketostix or ketone urine test strips. 4
In terms of what time of day to test for urine ketones, the most ideal time of day for urine strips testing on a ketogenic diet would be first thing in the morning.
First off, you probably have to make a trip to the bathroom. Secondly, you'll have accumulated ketone bodies throughout the evening that you can then measure in the early morning.
Doing so first thing in the morning is also probably the most convenient (which is the most significant factor) since you're probably in the comfort of your own home and having to pee first thing.
All you need to do is hold the keto strip in your urine stream and wait a few seconds for the result.
The cons with taking a ketone measurement via ketone strips is that as you become more adapted to using fats and ketones for fuel, your body will naturally expel less and less, which is a good thing.
Some individuals find that they experience high ketone levels on the urine strips (deep purple on the color chart) the first couple of weeks on a ketogenic diet. You may see these high readings early on because more ketones are excreted from the body due to its inefficiency at using them as a fuel source.
While urine testing may be the easiest of testing methods on a keto diet, it is often an unreliable way to check if you are in ketosis once adapted.
As time progresses, you may naturally see fewer and fewer ketones appearing on the test strips as your body becomes more efficient at using ketones. Fewer ketones are wasted, meaning less is excreted in the urine.When To Test For Breath Ketones
Breath ketone testing isn't as widespread as testing via a blood meter or urine test strip, and that's because breath testing is quite pricy initially.
The good thing about breath meters though, is there are minimal recurring costs and may be the least obtrusive method since it doesn't require any bodily fluids.
After starting a ketogenic diet, you may have noticed that you had a slightly sweet, almost metallic-like scent to your breath, similar to nail polish remover.
Don't worry; you weren't crazy… that's because your body expels a specific ketone body, more specifically acetone, from your breath when you're in ketosis. And you're also correct in thinking that acetone is a primary ingredient in things like nail polish or paint remover because it is.
In terms of the best time to test for ketones using a breath ketone meter, it may be best to either test first thing in the morning or after working out.
Ketone breath meters measure the number of ketones that your body is using and burning, so it makes sense to potentially get a reading after you've done some kind of activity.
If you're interested in using a breath meter, I've listed the two most popular ones below.
Are Ketones Higher In The Morning Or The Evening?
You may be wondering what time of the day will you generally see the highest ketone reading, morning, or evening?
From personal experience, I've generally seen the highest ketone readings first thing in the morning, but others have seen higher readings in the evening time.
That means there is no one right answer because different people experience different results.If you're someone who experiences a spike in glucose first thing in the morning (dawn phenomenon), you may find that your evening reading will be much higher.
You've also consumed food throughout the day, so it may make sense that for some people, they would experience a higher reading in the evening, especially after a high-fat meal or a meal rich in medium-chain triglycerides (MCTs).
How High Is Too High For Ketones?
The three ketone bodies are acetoacetate (AcAc), beta-hydroxybutyrate (BHB), and acetone. AcAc and BHB are produced from acetyl-CoA condensation, a product of the incomplete breakdown of free fatty acids (FFA) in the liver.
When following a ketogenic diet, a blood ketone level greater than 0.5 mmol L indicates you are in ketosis. This is accomplished by restricting carbohydrate intake severely, as is this case on a keto diet.
However, when ketone blood test levels register too high, this is referred to as diabetic ketoacidosis.
Diabetic ketoacidosis is defined as a blood ketone level greater than >10.0 mmol L in addition to high blood sugar levels. Basically, ketone production runs too high making the blood very acidic.
Diabetic ketoacidosis is a condition that occurs when there isn't enough insulin present in the body. This is generally the case with type 1 diabetes, when people do not produce enough insulin endogenously, and not common in those with type 2 diabetes or keto dieters.
Unfortunately, there is currently no way to measure this using urine ketone test strips or a breath acetone meter.
How Long After Eating Should You Check For Ketones?
I briefly mentioned it in one of the earlier sections, but you should generally wait for AT LEAST 3-hours after eating before you check for ketones.
Ideally, you'll want to wait as long as possible, but 3 hours is generally a good rule of thumb.You want to ensure that your previous meal has been digested and that any resulting rise in glucose and insulin of the prior meal doesn't alter your ketone reading.
For this reason, you should wait at least 3 hours, if not longer, before checking your ketones after a meal.
Do Ketone Levels Fluctuate Throughout The Day
Ketone levels fluctuate throughout the day as much as your weight may vary on a day to day basis.
It's perfectly normal for this to occur (both your ketones and weight).
You may even ben fluctuating in and out of ketosis throughout the day from doing normal daily activities or eating what you consider to be a keto-friendly meal.
But don't worry…
Just because your levels fluctuate, or you may be teetering out of ketosis now and then, it doesn't mean that you're not losing weight.
Does Drinking Water Reduce Ketones?
You may be wondering if drinking water or not drinking water has any effect on ketone levels.
It does, but only with a urine sample.
Being over-hydrated, dehydrated, and even taking certain medications can all affect ketone levels. 5
This is another reason why urine ketone testing may not be the most ideal or most accurate while following a keto diet.
If you're over-hydrated, then there's a strong chance you'll see a lower ketone reading. Being over-hydrated means the levels of ketones in your urine are diluted, thus showing a smaller concentration of ketones.
On the flip side, being dehydrated may show higher levels of ketones since the opposite is occurring, Being dehydrated means your urine will have a higher concentration of ketones, similar to why your urine is clearer the more hydrated you are and darker/more yellow when you're dehydrated 6
How Often Should You Test Ketones
How often you should test ketones is a matter of preference and what you're looking to accomplish.
First, let me state that the level of ketones present, regardless of which method you choose to use, does not correlate with the amount of fat you're losing.
This is why you may have heard the phrase, “chase results not ketones,” and that's because sometimes people get caught up worrying about the wrong things when it comes to weight loss.
Testing for ketones can be a great way to ensure you're on the right track or seeing how your body reacts to certain foods, but don't let it be the be-all-end-all to how you make decisions when it comes to your weight loss efforts.
Let the scale and mirror do that for you.
For those looking just to see whether they're on the right track, testing once a day or every other day may be adequate.
Those interested in testing how different foods or meals affect their glucose and ketone levels, then testing before a meal, and potentially 60, 120, and 180 minutes after would be insightful.
Therefore, how often you should test ketones is a matter of preference and what you're looking to accomplish.The truth is, you don't have to test at all if you don't want to, and for some, this may be the best option.
Testing can be an additional stress to some people, similar to weighing yourself all the time.
Just know that fluctuations are natural.
The Takeaway
The best time to test for ketones on a ketogenic diet is when it's most convenient to your lifestyle and when you can ideally check under the same type of conditions, so you have an accurate comparison.
Aside from that, test for ketones first thing in the morning before having anything to eat or drink or right before dinner, and ideally 3+ hours after your last meal.
Blood testing is a great way to collect personal data of both ketone measurements and your blood sugar level. You'll have a great indicator of whether you're in ketosis and can detect early signs of insulin resistance.
Frequently Asked Questions
How long does it take to test positive for ketosis?
After 12 hours of fasting the body's metabolic switch will flip. When moving towards hour 24 that's when the body enters the fat burning stage and the level of ketones will rise.
What is the most accurate way to test for ketones?
The most cost effective way of testing for ketones regularly is purchasing urine testing strips. However, the most accurate results are available through the use of a blood ketone meter.
What is a good ketone level for ketosis?
If you're 0.5-3 millimoles per liter on the ketosis meter then you're in a good ketone level for ketosis.