Ketogenic diets are increasingly popular as a strategy for weight loss, blood sugar control, and for a cognitive boost, but how can you tell if you’re actually in ketosis?
How to measure ketones
A ketogenic (keto) diet is low-carbohydrate, high-fat, and moderate-to-high-protein.
The aim of a keto diet is ketosis: a state where your body burns fat stores for fuel instead of relying on glucose (glycogen). A low-carb, high-fat, moderate-protein diet doesn’t always put you into or keep you in ketosis, though, and your diet may need adjusting to help you reach and maintain ketosis.
Ketones are protective, almost as a natural antioxidant circulating in the body. If you do a very high fat diet without the benefit of the ketones, you’re not getting the benefits and may be doing significant harm.
As ketosis is the goal of a ketogenic diet, you’re going to need a reliable way to know if you’re actually in ketosis. To figure that out you’ll need to measure ketones, also known as ketone bodies.
Ketosis vs Ketoacidosis
If you observe rising levels of ketones in your blood or urine alongside any of the following, seek medical advice to address the possible risk of ketoacidosis:
- high blood glucose levels
- excessive thirst
- frequent urination
- flushed skin or dry skin.
Ketosis is not a medical condition and does not require medical intervention. In contrast, ketoacidosis can be life threatening and should be addressed immediately.
Blood, breath, and urine tests for ketosis
Dietary ketosis increases your ketone levels, and this is detectable in breath, urine, and blood. Breath tests are currently quite imprecise and unreliable, so, for now, you’ll want to use one of the other methods to measure ketones: urine and blood.
Both urine and blood tests have long been used by people with diabetes to help keep track of blood glucose levels. These tests can help those with diabetes determine if their blood glucose is too high and if they’re at risk of ketoacidosis. This may sound like ketosis, but ketoacidosis is a complication of type 1 diabetes and a potentially life-threatening condition. In ketoacidosis, the body, in response to feeling starved, begins to break down fats and proteins too fast. Frequent testing allows a person with diabetes to adjust medication, diet, exercise, and other factors accordingly.
For those without diabetes and who want to follow a ketogenic diet, similar blood testing methods can be used to measure ketones. Be aware, though, that blood glucose test strips are not exactly the same as ketosis test strips.
Let’s take a look at how ketosis tests work and the advantages and disadvantages of urine test strip for ketosis versus blood tests for ketosis.
|Simple to use||Only measure up to a few hours earlier||More accurate||Slightly more involved|
|Affordable||Not helpful once you’re keto-adapted||Best option after keto-adaptation||More expensive|
|No needles!||Shorter shelf life||Longer shelf life||Needles!|
|May be affected by hydration, food consumption, and recent exercise||Less likely to be affected by hydration, food consumption, and exercise.|
Measuring ketosis using urine test strips
Urine strips are a convenient and relatively inexpensive way to find out if you’re in ketosis or at least heading in the right direction. These strips are available over the counter at pharmacies, grocery stores, and online. Boxes typically contain 50 to a couple of hundred or so strips.
For those of you who, like me, love a good bulk buy discount, bear in mind that these strips usually expire within three to six months of being opened. So, be sure you’ll use all the strips before you buy and/or open a box.
There are a few other disadvantages to using urine strips to measure ketone levels. Urine ketone concentrations can be affected by how hydrated you are (and, thus, how concentrated your urine is in general) as well as by recent exercise (and sweating) and even recent food consumption. Additionally, urine test strips typically only measure acetoacetate, one of three ketone bodies. Beta-hydroxybutyrate is the more common ketone body produced, but urine tests don’t measure BHB.
Still, urine test strips offer a simple and inexpensive way to see if things are headed in the right direction.
How to test urine for ketones
To use a urine strip to test for ketosis, it’s best to measure at the same time every day. This could be first thing in the morning or right before bed. To use a strip, avoid touching the spongy end of the strip and follow this procedure:
- Wash your hands
- Use a sterile container (a small Mason jar works well) to collect a urine sample
- Immerse the absorptive end of the test strip into the urine for a few seconds, then remove
- Wait for the strip to change color – follow the test strip instructions for how long to wait
- Check the color of the strip against the chart on the product packaging
- Ignore any changes to the color after the number of seconds indicated on the packaging
- After testing, dispose of the strip and wash your hands.
In general, the darker the color of the strip, the higher the level of ketones in your urine. Be sure to test the strip against the color chart provided with the strip, however, as strips may differ slightly between brands.
Using blood to measure ketosis
Blood tests are far more reliable and accurate than urine test strips for measuring ketosis. As noted earlier, ketone blood meters were originally created to help those with diabetes to properly manage blood glucose levels and prevent ketoacidosis.
Blood test strips can be found at pharmacies and some grocery stores. Unlike with the urine test strips, however, you’re going to need a meter to read the blood test strips. These meters are designed to read blood glucose test strips, with some meters also able to read blood keto strips.
Blood keto strips cost around $1 per strip. They have a shelf-life of around a year to 18 months once opened, making them longer lasting than urine test strips.
How to test blood for ketones
To measure your blood ketone levels, follow this procedure:
- Wash your hands
- Follow the package directions to load the lancet with the needle
- Insert a blood ketone strip into the meter
- Use the lancet to prick your finger, drawing a small drop of blood
- Place the test strip against the blood for a couple of seconds (some strips require more blood than others)
- Wait for the meter to display the results
- Follow the directions to safely dispose of the strip and lancet (use a sharps container for safety).
It’s best to measure blood ketone levels at the same time every day, ideally first thing in the morning after fasting overnight.
How to interpret blood ketone results
If you’re in a state of dietary ketosis, blood ketone test results will usually fall between 1.5 and 3.0 mmol/L. This equates to 15-300 mg/dL. 1
Let’s break it down further. General guidelines, care of Diabetes UK, are as follows:
- Under 0.6 mmol/L – normal blood ketone level
- 6-1.5 mmol/L – higher ketone levels than usual
- 6-3.0 mmol/L – high ketone levels; very likely in ketosis, but poses a risk of ketoacidosis
- 00 mmol/L or higher – a dangerous level of ketones; requires immediate medical intervention.
During nutritional ketosis, blood ketone levels may be in the range of 0.6-3.0 mmol/L. The trick is to know your own baseline and assess accordingly.
Now, let’s assume that you’ve been following a ketogenic diet for a few days or weeks. It’s not uncommon to see your urinary ketone levels rise initially, only to see them start falling again after a few weeks. Why? Keto-adaptation.
Be aware of keto-adaptation
After a few days on a ketogenic diet, most healthy individuals will enter a state of ketosis as their body produces more and more ketones. In those first few days and weeks, your body will struggle to use ketones as a source of energy. This means that you’ll be eliminating a lot of ketones in your urine, which can be measured using the right kind of ketone urine test strips.
As your body becomes keto-adapted, it gets better at using ketones as fuel. This means that lower levels of ketones are excreted in urine. 2 By the time you’ve been on a ketogenic diet for a few weeks or months, chances are that your urine contains only very small amounts of ketones. This doesn’t mean you’re not in ketosis, however.
So, if you’ve been eating a consistently ketogenic diet and measuring ketones with urine strips, watch for an initial rise in ketones, a plateau, and a drop in ketones. This is the point where switching to blood test strips makes most sense. 1
Put simply, urine strips are a great option for the first few weeks. Afterwards, however, blood test strips are a far better choice for measuring ketosis. Using blood test strips right from the get-go is unnecessarily expensive, however, and means you’ll be pricking your finger a lot. Once you’ve got the hang of a ketogenic diet, you’ll know how it feels to be in ketosis and can simply use the occasional blood test strip to check where you’re at.
Blood keto meters
Not all blood glucose meters can read blood ketone test strips, so be sure to check before you buy. In addition, some meters only work with test strips from the same company and some meters require a subscription and/or a phone app to monitor and access your results.
The Keto-Mojo is one of the best options for testing blood glucose. Each pack of Keto-Mojo Ketone Test Strips contains 50 blood keto strips and costs $50. The control chip is in the bottom of the box, not in the vial with the strips, so be careful not to throw the box away! Also, be aware that these test strips only work with the Keto-Mojo meter, so you’ll have to first purchase the full kit ($60) which includes the lancet device, 10 lancets, and a meter. An easy-to-understand video is provided to make sure you use the kit correctly.
Abbot and other companies also make blood ketone meters, but their test strips are often exorbitantly expensive (up to $3 a strip!). So, before you buy a meter, check the price of the corresponding test strips.
Urine keto strips
As for urine ketone strips, some can test both for glucose and ketones in urine, reflecting levels up to a few hours prior. Perfect Keto Ketone Testing Strips are a good option. Each package provides 100 strips (around a three-month supply) and costs around $8. The bottle has a handy color chart on the side and is discreet and compact enough to carry with you for use on the go.
If you’re sharing a pack of urine strips with someone else or plan on taking a measurement more than once a day, consider the more cost effective 150 pack from One Earth Health. At $6.99 for 150 strips, this pack represents far better value, but only if you’ll actually use the strips within the 90-day expiry window.
In summary, urine test strips are a great idea for those just starting or returning to a ketogenic diet. They are inexpensive, easy to use, don’t require poking yourself with a needle, and can help you figure out if you’re heading in the direction of ketosis. This lets you adjust your diet accordingly to increase the likelihood of ketosis.
Once you’re actually in ketosis, blood strips are the way to go, especially once your body becomes keto-adapted.