How To Tell If You’re In Ketosis: What Works and What Doesn’t

Let’s start with the basics…

If you eat a ketogenic diet - typically high in fat and protein, and very low in digestible carbs - you’ll reach a state of ketosis. Which means, your body will be utilizing significant amounts of ketones to fuel your energy needs.

The benefits of ketosis are clear. Lower inflammation, greater insulin sensitivity, improved cognitive functioning, and more. But if you’re new to keto dieting, you may find yourself wondering if you’re actually eating a ketogenic diet.

Keto diet

Here’s the good news...

It’s easy to determine if you’re in ketosis. You just need the right knowledge. And as we’ll learn, the ability to measure your level of ketosis will give you a very real super power. So keep reading, because we’ll tell you everything you need to know about measuring ketosis.

How Do I Tell if I’m in Ketosis?

To maintain ketosis, you need to stay consistent with your diet. Even a seemingly small mistake can disrupt ketosis and prevent you from enjoying the full benefits of a ketogenic diet. But some of us who are new to keto dieting are not always sure if we’re doing it right. So the most important question becomes…

How do I tell if I’m in ketosis? 

how to tell if I'm in ketosis

The answer is ketones. When you eat a ketogenic diet, you’ll produce a measurable amount of ketones. So by measuring your level of ketones - you can definitely measure your level of ketosis!

Keto Breath: A Sign of Ketosis

Before we cover how to accurately measure blood ketones, let’s talk about some telltale signs that your body is in ketosis. We’ll start with perhaps the most popular keto condition - that’s right, we’re talking about keto breath

What is Keto Breath?

Keto Breath is a temporary condition that occurs when a ketogenic diet is done right. It’s characterized by having a breath odor that closely resembles that of nail polish remover. And that makes perfect sense, because a key ingredient in nail polish remover - acetone - is exactly what you’re exhaling in the case of keto breath! 

In a state of ketosis, your body is breaking down fats to produce ketones. Most of these ketones are metabolized to fuel your energy needs, but some are lost in urine and breath. And one ketone that is mostly lost in exhaled breath guessed it...acetone! 

Now, you may think that keto breath is too awful to endure as the price of admission for a ketogenic diet. But here’s some good news - keto breath is 100% temporary

So...even if you notice a particularly bad case of keto breath early on in your keto journey - keep going! Your body will adjust to low-carb dieting and free you from keto breath - once and for all. 

Keto Breath Meters

While your breath odor may return to normal, your body will continue to remove ketones during exhalation. And that’s great! Because it means we can measure the ketones exhaled in your breath - and use that value to approximate the circulating blood ketones in your body! 

Now, before we talk about keto breath meters, we need a quick disclaimer. Measuring exhaled ketones is NOT the best way to quantify your state of ketosis. The best way is using a ketone blood meter (more on that later). But we do know a keto breath meter that is fairly useful at giving you an approximation of your blood ketones. And here it is…

Biosense Ketone Breath Meter

BioSense is truly the only ketone breath meter we’ve tested that’s anywhere close to the accuracy of a ketone blood meter. And because a breath meter is easy and non-invasive, it might be a good option for those who are particularly squeamish around blood.

The table below outlines readings from my BioSense meter compared to readings from my Precision Xtra ketone blood meter. These readings were taken within minutes of each other, so they are both quantifying the same exact state of ketosis.

For reference, the “ace” is a made-up unit of measure that the BioSense meter uses.

BioSense Ketone Breath Meter

Precision Xtra Ketone Blood Meter

5 aces

.9 mmol

4 aces 

.9 mmol

3 aces

.5 mmol 

3 aces

.3 mmol

2 aces 

.2 mmol

3 aces 

.2 mmol

3 aces 

.2 mmol

1 ace

.2 mmol

2 aces

.2 mmol

As you can see, the BioSense meter results track fairly well with my ketone blood meter. Which means, it
can be used as a tool to approximate your state of ketosis. So if you’re at all uncomfortable using a blood meter, the BioSense is a great option! 

And if you’re thinking, “can’t I also measure ketones in urine?”, then please definitely keep reading. Because I’m about to tell you why that’s a not-so-great option. 

Ketones in Urine: How NOT to Measure Ketosis

If you’re in a hurry, here’s the short story...

Ketone urine strips are worthless.

Keto Meter

Pictured: a set of tools that are as useful as ketone urine strips for measuring ketosis

If you commit to a ketogenic diet, you will have ketones in your urine. That much is true. But measuring these ketones is worthless - because the amount of ketones in your urine doesn’t really tell you anything about how ketones are being made and processed in your body.

Firstly, the concentration of ketones in your urine will be heavily influenced by external factors - including, most notably, your level of hydration. That means you could have the same value of circulating blood ketones, but register wildly different ketone urine readings depending on how much water you drank that day! 

For that reason alone, you should avoid ketone urine strips. But if you need another reason, here you go...

Over time, as you maintain your ketogenic diet, your body will become more efficient at metabolizing ketones for energy. Meaning, less of the ketones you produce from fat will be lost in urine. This means that as you move deeper into ketosis, your ketone urine strip results can actually trick you into thinking you’re no longer in ketosis!

Now, this is the time where most articles would promote some ketone urine strip brands that you could use. But if you paid attention to the above, you’ll know that ketone urine strips are worthless. So let’s skip the product options, and move straight to the most important thing you’ll read all day…

How to ACTUALLY Measure Ketosis: The Ketone Blood Meter

There’s only ONE way to truly measure your state of ketosis. And that’s with a ketone blood meter.

We’ve tested dozens of ketone blood meters, and we’ve found that the most accurate and consistent meter is the Precision Xtra by Abbott. This meter will allow you to accurately measure your blood ketone and glucose values - and the pairing of this data will tell you what you need to know about your level of ketosis.

For a quick tutorial on how to use the Precision Xtra, check out this video from our friend Keto Diet Results.

And once you’re an expert on using the meter, here’s a quick guide to what the numbers mean. 

Reading Blood Ketone Values

While there is some debate over the accepted range for ketone values, here are some standards to go by:

<0.5 mMol: This range is typical for people eating a “non-ketogenic” diet. If you’re not restricting carbs, don’t expect to see your ketone value rise above 0.5 mMol too often.

0.5 mMol - 1.0 mMol: This is the standard range for what’s called “light ketosis”. If your reading is in this range, good job! You’re producing significant ketones. 

>1.0 mMol: A ketone blood value over 1.0 mMol is typically defined as deep ketosis. After a couple of weeks on a ketogenic diet, you should be frequently seeing ketone values over 1.0 mMol. 

However, the ketone value alone isn’t the only thing that matters. You also need to pair the ketone value with your glucose values.

Reading Blood Glucose Values

As shown in the video above, you can use the Precision Xtra to measure blood glucose as well. This is important, because the pairing of blood ketones and glucose is what truly allows you to measure ketosis. 

While there’s no standard range, there are some general reference ranges when it comes to blood glucose. Those on a ketogenic diet will typically register a blood glucose value below 80 ng/ml. While those on a standard diet will typically register a blood glucose value at or above 80 ng/ml.

Thus, if you want to tell if you’re in ketosis, here’s what to do. 

  1. Measure your blood ketone and glucose values

  2. If you have a blood ketone value over .5 mMol and a blood glucose value around or below 80 ng/ml - congratulations! It’s safe to say that you’re in ketosis.

This is the strategy I’ve been using for years. And it’s truly the only strategy you need to quantify your level of ketosis. And as you continue to measure, you’ll gain a real super power. Before you even take out your meter, you’ll be able to see into the future. 

Here’s what I mean… 

Measuring blood glucose and ketones not only tells you exactly what you need to know about your metabolic state - it also gives you real insights into how different foods and eating schedules affect your metabolism. And as your experience with keto dieting grows, so does your ability to intuit the state of your metabolism. 

Take me for example, I’ve been measuring blood glucose and ketones for years. So at this point, I don’t even need to measure. I know my body, and how it reacts to different foods and fasting schedules. And so, without using a meter, I can tell you with real accuracy what my blood ketone and glucose values will be.

ketone level of ketosis

Pictured: an experienced keto dieter looking into the future.

It’s not quite invisibility or super-strength, but if you’re committed to living a keto lifestyle, seeing into the future is a useful super-power. And once you’re aware of how ketone and blood values change over time, here’s another thing to be aware of...

More Muscle. Lower Ketones. 

If you continue to eat a ketogenic diet, you’ll notice that - over time - your ketone readings will go down. That’s because your body becomes more efficient at metabolizing ketones over time. And this is especially true if you have more muscle! 

Muscle tissue is more metabolically active than fat. Meaning, your muscle tissue requires a higher energy input than your fat tissue to maintain itself. So...if you’re someone with a lot of muscle and low body fat percentage, you’ll be burning more energy at rest than someone with a higher body fat percentage. 

(Side note: if you’re looking to build muscle on a ketogenic diet - check out our article: Building Muscle on Keto)

This is yet another reason to avoid any feelings of “ketone envy”. Don’t get caught up trying to have the highest ketone value possible. Remember, there is more to ketosis than simply your level of circulating blood ketones. You also have to consider your ketone utilization.

And don’t get discouraged if you see your blood ketones decline over time. This is not only normal, but most likely a sign that you’re lowering your body fat percentage and moving toward a healthier body composition! 

keto body builder

Remember: if your body looks like this, it's OK if you're ketones are lower :)

Validating your Ketogenic Diet

At this point, you’re an expert in measuring ketosis. You know how which meters are accurate (Precision Xtra ketone blood meter and/or BioSense breath meter), and which meters to avoid (any urine strips). And with this knowledge comes an invaluable skill…

You can now tell when companies are lying! 

Many brands claim their products are ketogenic or “keto-friendly”. But hardly any of them have the data to back those claims up. So we at Legendary Foods propose a challenge… 

  1. Measure your blood ketones and glucose. Ensure that you’re in ketosis. 

  2. Eat any legendary product, and…

  3. Measure again. 

I did this several times with our new Low Carb Tasty Pastries and found no change in my numbers. I expect you’ll find the same.