Measuring Ketosis With Ketone Strips: Are They Accurate?

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Picture of a Container of Keto Strips Bottle With Color Chart.Many people following keto diets want to be in ketosis, a natural state in which the body burns fat for fuel.

For this reason, people are curious about whether they are doing enough (via carb restriction) to achieve this state.

As a result, ketone strips are a popular tool that numerous people use as a way of measuring ketosis.

However, just how accurate are they?

And how do they compare to alternate methods of measuring ketones?

What is Ketosis?

Anyone following a standard high-carbohydrate diet will be burning glucose for energy.

However, the body can use both carbohydrate and fat for fuel (1).

When carbohydrate intake is very low, the body switches to burning fat for energy. As this happens, our body enters a state of ketosis.

Ketosis is a natural biological state during which our body burns fat for fuel. While we are “in ketosis,” our blood levels of ketones—a by-product from the breakdown of fats—rise.

Measuring these ketones (also known as ‘ketone bodies’) can, therefore, provide a hint as to how deeply our body is (or isn’t) in ketosis.

For this reason, ketone strips—which measure the level of ketones—have become increasingly popular in recent times.

Key Point: Ketosis is a biological state where the human body burns fat rather than carbs.

What are Ketone Test Strips?

For people who want to know if they’re in ketosis, ketone test strips are a cheap and simple way of detecting ketone levels.

They are otherwise known as ‘ketone sticks’ and work by urinalysis to tell us the volume of acetoacetate in our urine.

If you don’t know what acetoacetate is, then let’s start at the beginning.

First of all, there are three types of ketone body;

  • Acetoacetate

Chemical Formula For Acetoacetate - a Ketone Body.

Acetoacetate is one of the two main ketone bodies, and it is present in urine.

We can test for it by using ketone strips.

  • Beta-hydroxybutyrate

The Chemical Formula for Beta-Hydroxybutyrate.

Beta-hydroxybutyrate is created from acetoacetate, and it is the second of the main ketone bodies.

This ketone body shows up in our blood, and blood ketone meters can tell us the volume.

  • Acetone

Chemical Formula For Acetone - a Ketone Body.

Acetone is also a ketone body, although not as prevalent as acetoacetate and beta-hydroxybutyrate.

The breakdown of acetoacetate produces acetone, and it is present in our breath.

How Do Ketone Strips Work?

You can probably guess the finer details, but if you want to know how to use ketone strips, the process looks like this;

  • Take a urine sample in a clean container/jar of some sort
  • Hold the end of the strip in the urine for a few seconds
  • Shake the strip to remove any excess “liquid” before removing from the container
  • Wait 15 seconds until the ketone strip changes color
  • Comparing the color of your ketone strip to the color chart will let you know if you’re in ketosis (and how deeply).

Here is a video of someone doing it;

Knowing how to read the ketone strip is important too, so here is the color chart;

Picture of a Color Chart on a Ketone Strips Container.

The color on the far left means that no ketones are present, and the pink colors signify a light to medium state of nutritional ketosis.

As we move further to the right, the darker purple shades suggest a very strong level of ketosis.

 State of Ketosis Ketone Level (mmol/L) Ketone Level (mg/dL)
 Very light0.1 – 0.51 – 5
Light0.6 – 1.56 – 15
 Medium1.6 – 3.016 – 30
Strong3.1 + 31 +
Key Point: Ketone test strips are a urinalysis tool. They give people an indication of their state of ketosis by showing the level of ketones in urine.

What Level of Ketone Bodies is Best For Health?

For those aiming to be in ketosis, what kind of reading should we strive for?

I have a feeling that many will look at the table and automatically assume that ‘strong’ is best.

However, for the average person just looking to take care of their health—or maybe lose some weight—higher levels are not necessary at all.

If you’re in the ‘light’ range, then your body will be burning fat for fuel, and you’ll have ketone levels that are many multiples of the average person.

In short, aiming for a random ‘optimal’ ketone number isn’t the right approach.

Listening to your body and seeing how you feel? That’s the right way to go about it.

Note: If you are undertaking a ketogenic diet for a medical purpose, speak to your physician about this. Therapeutic ketosis levels may be very different to what the average person needs.

Key Point: Higher ketone levels are not necessarily better. For the average person, light/moderate ketosis is perfectly fine.

How Accurately Do Ketone Strips Measure Ketosis?

On the negative side, ketone strips are not always as accurate as most people believe.

For example, here are a few circumstances in which an inaccurate reading could be possible;

Picture of a Male Human Body's Silhouette.Ketones in Urine Don’t Give a True Indication of What’s Happening in the Body

In the first place, any ketones which go unused by the body are excreted via urine (2).

To put that differently, urine strips only show the number of excessive ketones that our body couldn’t use.

Therefore, just because the level of ketones in urine is small doesn’t mean that the levels in our blood are also small.

Nor does it mean that we are not in ketosis.

For this reason, blood ketone levels are a more accurate way of measuring ketosis than ketone test strips.

Hydration – Does Over/Under Hydration Affect Ketone Levels?

First of all, this idea relates to how well hydrated (or dehydrated) someone is, and whether this state impacts the ketone strip reading.

For instance, if someone is drinking large amounts of water, then it may dilute urine to the extent that affects the reading.

On the other hand, if someone is dehydrated, then higher concentrations of ketones may be present.

However, I’m not convinced that hydration greatly impacts the reading.

Ketone strips are designed for the average person consuming typical amounts of water. If someone is seriously dehydrated or drinking extreme amounts of water, then yes… this may potentially impact the reading.

But for the average person, I don’t think hydration should significantly affect these readings.

Picture of a Happy Woman Holding an Avocado.Keto-Adaptation

It takes time to adapt to burning fat for fuel.

For example, you may have heard about the ‘keto flu.’

This particular name refers to the often uncomfortable period during which the body learns to use fat for fuel rather than glucose.

In other words, when someone first starts a ketogenic diet, the body won’t be using ketones efficiently (3).

As a result, it’s likely there will be a higher concentration of waste ketones in the urine in the initial stages.

Over time and as the body adapts to burning fat for fuel, it should become more adept at burning ketones for energy. As this happens, the volume of ketones we excrete will fall.

Consequently, ketone readings may go down at this time.

This disparity may be confusing since your body will be more in ketosis, yet with a lower level of ketones showing on the ketone strip.

It is a reason why ketone sticks don’t tell the full story and why their accuracy isn’t always reliable.

Key Point: Ketone strips are not always 100% accurate, and the readings may fluctuate for a number of reasons.

What Are Some Other Ways To Measure Ketones?

There are three main ways of measuring ketones in the body;

  • Blood meters (beta-hydroxybutyrate)
  • Breath analyzers (acetone)
  • Urine strips (acetoacetate)

As we have already gone through the latter, let’s look at the other two methods.

Ketone Blood Meter

Picture of a Lady Next To a Ketone Blood Meter With Blood on Her Finger.

Ketone blood meters are more accurate than testing by urine strips.

However, this extra accuracy comes at a higher price.

How do blood ketone meters work?

  • First, you need to insert a blood ketone strip into the ketone meter.
  • After this, prick your finger to draw some blood (don’t worry, it’s just a small drop like a standard blood glucose test).
  • Put the blood on the ketone strip and check the results.

This technique is simple, and as previously mentioned, levels of ketones in the blood give a more reliable indicator of ketosis than urine levels.

Breath Ketone Analyzer

While ketone breath analyzers don’t offer the same accuracy as blood meters, they have some positive points;

  • The initial purchase of the equipment is more expensive than ketone strips, but it’s a one-time deal. No more purchases are necessary. Unlike the other two methods, you can re-use the breathalyzer as much as you want. It’s by far the most cost-effective way of measuring ketones.
  • It’s straightforward to use and doesn’t require urine or blood.

How do breath ketone analyzers work?

They are very simple.

All you have to do is turn on the breathalyzer and then breathe into it for however long the manufacturer instructs (about 15 seconds).

Wait for a few seconds and then check the results.

Key Point: Blood ketone meters and breath ketone analyzers are more accurate than ketone strips.

What is the Best Way To Measure Ketosis?

This question has no clear answer, and it depends on what you’re looking for.

  • Breath Ketone Analyzer: Expensive, but you only pay once since it needs no ketone strips. Probably somewhere in the middle when it comes to accuracy.

Final Thoughts

Ketone strips are a reasonably accurate—and cheap—way to detect someone’s (approximate) state of ketosis.

For someone attempting to ‘enter’ therapeutic levels of ketosis, ketone testing is a valuable tool.

However, they are probably not necessary for the average person who just wants to lose a bit of weight or finds a keto diet beneficial.

That said, they can be a useful way to check that those new to ketogenic diets are on the right track.

For information on when excessive ketone levels can be an issue, see this ketoacidosis guide.

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  • Inaccuracy issues with keto strips do make sense. After all, the urine is never the truest indication of what’s going on in our bodies. It can help but it seems that the results should always be considered carefully.

  • The inconsistencies is these strips somewhat discourage some of us in using them because one can never tell ABSOLUTELY if they are right on point. All the same, I think they are pretty darn useful. Thanks for sharing this info Michael

  • Thank you very much! I was searching around the internet for “just simply stated” information and found it here. And another thank you for the Ketone Level Chart. Added it to my phone for ready reference at a glance!

  • I have been on a Keto diet for 8 weeks and I have lost 12 pounds. My Keto sticks always register negative. I figure if I am eating Keto foods and losing weight then I should not worry about the test strips. Your thoughts?

    • Absolutely, 100% agree. If you are losing weight and feeling healthy then that is the most important thing, not some random number.

      Well done on your progress too – 12 pounds in 8 weeks is great!

  • I started the diet a month ago and tested for the first time today with urine strip. At (or above) 16 mmol/L. Far side of the stick. Still quite lethargic and even at times weak. I have lost weight and inches (quite a bit for 4 weeks), but am not eating much (compared to my prediet intake) due to small appetite and may be losing weight for that reason alone? I thought I would be adapted by now, but with reading this high in urine, is it likely I am not burning fat/ketones yet? I am not diabetic or prediabetic as far as I know. Should I worry about how high the number is this far into the diet?

    • Quite a lot of points here!

      1) As stated, ketone strips can be unreliable… and it would be irresponsible of me to try to guess your exact situation, so if you have any concerns at all then I would recommend seeing a doctor and explaining everything and getting a quick check-up.

      2) The weight loss is absolutely because of eating less. Generally, this is one of the positives about ketogenic diets; they seem to be really beneficial for satiation and people naturally reduce their total food consumption. Not always, but often.

      3) Feeling weak/lethargic after 4 weeks isn’t good. As you said, it could be as because you are eating far too little calories, or it could just be that a ketogenic diet doesn’t really fit you. There’s no one diet to rule them all, and some people do better with a slightly higher carb intake.

      • Hi Michael. I’ve been on the keto diet for just over 2 weeks now. I lost 7 lbs the first week and my urine test strips were in the mid range. During the second week, Like Leah, my urine test strips have been off the charts and I am very weak and dizzy. I haven’t changed my diet and I’ve lost another 3 lbs, eating plenty of fat and following lots of keto recipes. Should I just give it more time in hopes of my energy returning? If I try eating more carbs, should I reduce my fat intake? I want to live a keto lifestyle to lose weight and maintain good health but it’s scary the way I feel right now…like when you’re on diet pills that make your heart race with any exertion. Do you have any advice on what I could tweak to bring my ketone stick levels into the mid range again (3) and regain energy?

        • Hi Diane,

          I can’t give personalized advice, but here are some general things that people should be aware of:

          1) Ketogenic diets can have positive effects, but they aren’t the right fit for everyone – some people do better with more carbs.

          2) Some people don’t eat enough food when they switch to a keto diet – they cut carbs, but don’t properly replace them with enough fat/protein.

          3) So-called “keto flu” can cause people to have certain side effects such as dizziness and lack of energy – consuming enough electrolyte minerals is important when people start ketogenic diets (https://www.nutritionadvance.com/keto-flu)

        • A few years ago, I was eating Keto. Felt great most of the time. At one point though, I get exhausted and lethargic. I went to my doctor and found I was anemic due to a lack of folic acid and vitamin b. I adjusted my diet to be carb light, not carb free by adding more fruits and vegetables with essential vitamins I needed. Michael is right, it’s all very personal, not one size fits all. I advise that you listen to your body, check in with your doctor and adjust your diet to what your body needs to operate best.

  • Hey Michael, thank you for sharing the information, a great read!
    I’ve been using keto strips, and I realized that if I leave my tested strip out longer(say one minute), it becomes much darker–why is that? It makes me from being in very light ketosis(0.5) to light state(1.5 or more). Can you shed a light on this? This makes me question the accuracy of the strips, but also brings me hope…haha…

    • Thanks!

      To be honest, I don’t know the exact reasons they get darker with longer lengths of time… but this is a common thing and always happens. As the pack will probably say, depending on the brand, an accurate reading will be given at 15 seconds! So, whatever color it is at that time will be the (most) accurate reading.

  • Been on a ketone diet 10 days now dropped 11lb so over the moon my levels are showin +++80 I just wanted to use strips to check I’m doing my diet right and they worked for me as they are showing what I expected for my results did have the bad head first two days but energy levels and me feeling great at the minute.

  • Hi and thanks for the advise , I got my Keto urine strips today and they say I’m at 8🤔I feel great have more energy and have lost 7 pounds in 5 days but IDK

  • Hi Michael,

    I started my keto diet 10 days back , starting from keto Reboot and continued on a strict low carb diet…I have lost 5.6 kgs and feel energetic..just to test whether I was in the state of ketosis I bought ketostix and measured the level…most of the times I am getting the level of 80++ initially j was happy about it but when I went to internet it’s mentioned that it might be an indication of diabetes and other things like coma and higher level might proved fatal…please clarify?

    Thanks

    • Hi Rajan,

      It sounds like you were reading about something called ‘diabetic ketoacidosis.’

      This is a potentially life-threatening condition that affects people with type 1 diabetes.

      On the other hand, ketosis (in a healthy person) is very different. You can see a comparison between the two here: https://www.healthline.com/health/ketosis-vs-ketoacidosis

      If you have any concerns about T1D or anything else, please see your doctor/healthcare team, explain about your diet and get tested. It is always better to be safe and sure.

  • Why do my ketostix always come up negative? My carbs have been kept below 30g/day and I’ve lost over 50lbs in less than 90 days I just don’t understand why the ketostix are not showing a positive reading.

    • Not sure – that sounds strange. Did you follow the product instructions exactly?

      But either way, it is the outcome that is most important. If you are losing weight and making progress, then that is much more important than any random strip reading.

      • yes it doesn’t make any sense! I have tried both “Ketostix” and “True plus” Ketone test strips. both just opened with expiration dates of 12-31-2019 and 11-30-2019 respectively. I’ve used both with urine stream and sample cup methods and in every test it comes out negative. I ordered a blood ketone meter to see if I can get a reading that way. Is it possible my body has adapted and is using fats that efficiently or so completely to the point ketones in my blood just aren’t being expelled in my urine??? And is that a bad thing? I’m literally drinking gallons of water and taking potassium and magnesium supplements too. an average day is 1600 calories w/16g carbs, 125g fat, 95g protein, and sodium around 2800mgs. and my urine stream is very yellow most of the time. I just want to make sure I stay in ketosis so I don’t have to worry about muscle loss from reduced caloric intake. I have to add that a much as I enjoy a really good pizza I find fatty foods the most satisfying by far.

        • It could be like you said, and no that wouldn’t be a bad thing – it would just mean that your body is utilizing everything efficiently. However, I would still expect there to be at least some kind of positive result. There is also the issue that sometimes these strips can be unreliable, but if you have tested multiple times with different brands then this should be irrelevant. If you really wish to know, it might be worth taking a blood ketone test since this is more accurate.

          If worried about muscle loss, I would say increasing protein intake would be the most evidence-based way to prevent catabolism.

          • yes but wouldn’t or couldn’t that (increased protein) be counterproductive with a LCHF diet since the body could actually convert proteins into carbs by a metabolic process called gluconeogenesis ? (just something I read) The blood ketone test kit I ordered will check Glucose also. My carb,fat,protein intake does change every day and some days my protein could be higher than my fat intakes too. I did an Atkins style low carb diet many years ago and went into ketosis quickly. Although I am losing weight this time as well I am having a hard time trying to figure out why I don’t seem to be in ketosis……….or at least why the ketone test strips keep coming back negative. I wish there was some common liquid like vinegar or something that you could just use to test the ketostix……! I’ll let you know how the blood ketone test works for me.

  • Been doing keto for a month and lost 16lbs just got my urine strips today and they say I’m in the high range(80) not sure if that good or bad?

  • I started Keto almost 4 weeks ago. I have lost 15 lbs and stalled but have gone down a size on the stall. The Keto urine strip is always the same color moderate that really dark pink 4.0 range. Is that ok? I mean after reading your article I probably should just toss them. I did notice that when they are in the garbage the next day they are dark purple. Is it the same rule of thumb don’t read them again after initial result? Thank you!

    • Hi Jay,

      Yes, if that is what you are aiming for. The test strips will show their most accurate reading after about 15 seconds, so anything after that will be unreliable.

  • I started keto around beginning of September and have lost about 13 pounds. I did a cheat day yesterday and had probably 100 carbs. and normally I never go over 50. I’m really good with this diet. But my keto level measured negative today. is this bad? Am I no longer in ketosis now?

    • Hi Leiah,

      There are a few points in regard to this;

      1) The readings can sometimes be inaccurate.
      2) If you lower carbs again then the ketone readings should quickly go back to whatever they were.
      3) Being “in ketosis” is just a natural process that happens when carbs are very low, but that doesn’t mean we need to be in it all the time. There is a lot of confusing information about this online, but if the diet is consistently working for health/weight loss, then that is much more important than ketone levels.