Ketone Strips: How Best to Test for Ketosis

If you’re on the ketogenic diet, getting to and staying in a state of ketosis is the name of the game. The faster you can achieve ketosis, the less likely it is that you’ll have to suffer the symptoms of “keto flu.” Being able to measure your ketones on the spot is a great way to monitor that journey. Enter: ketone strips. Let’s figure out how these strips work, where to get them, and how to use them.

The Keto Diet and Ketone Levels

The keto diet is a high-fat, moderate-protein, low-carb diet. It works to retrain your body to burn and process fat for an energy fuel source rather than sugar. You can turn yourself into a fat burner by dramatically limiting your carb intake and replacing those daily calories with calories from primarily healthy fats and some protein. 

When your body switches from glucose (sugar) for energy to ketones (from fat), you not only get health benefits like improved blood sugar control (a huge factor in preventing the development of type 2 diabetes), but you’ll also experience weight loss of a good deal of body fat, which improves your cardiovascular health drastically. There is even evidence that ketosis can help you live longer.

Once you reach ketosis and your body is effectively breaking down your stored fat into ketones (and fatty acids), there will be evidence of ketones in your breath (causing the dreaded keto breath at first), blood, and urine. You can measure levels of these ketones to see just how effectively your fat-burning efforts are going. 

To maintain ketosis however, most diets need adjusting, and monitoring the fluctuations of your ketone levels is a great way to do that. Ketone test strips for blood and urine are two of the options we’ll explore below, along with a breath monitoring device.

Ketone Strips: How Best to Test for Ketosis

There are two ways to use ketone strips for fluid testing, and another way to measure your breath. We’ll go in order of accuracy—blood, urine, then breath—plus provide all the details for using ketone strips: how to read, buy, and dispose of them.

Ketone Blood Test Strips

Ketone blood meters are the most accurate way to measure your ketone levels at home (i.e., outside of a laboratory or medical setting). Blood testing strips were initially designed to help those with type 1 diabetes regularly test their blood sugar levels with a small amount of blood and minimal pain from needle sticking, and that technology has also been utilized for measuring blood levels of ketones (to help diabetes patients check for the life-threatening condition diabetic ketoacidosis).

You can often find ketone blood strips available anywhere that ketone urine strips can be purchased, though both require a meter to interpret and measure the biological information. Interestingly, most blood glucose meters can read the keto strips as well: a glucose strip will give you a glucose reading, while a ketone strip will measure your ketones.

At about a dollar per strip, keto blood testing strips are more pricey than urine testing strips, but with an expiration date between a year to 18 months (which is considerably longer than that of urine test strips). To operate a blood ketone meter:

• First, wash your hands.
• Load a blood ketone strip into the meter.
• Follow the instructions for how to use the needle and lancet.
• Prick your skin to draw a small amount of blood.
• Place the blood in contact with the strip and wait for the results.
• Properly dispose of the lancet and the strip.

Ideally your result for blood ketone levels will be between 1.5–3.0 millimoles per liter (mmol/L). If it’s not in that range, you may want to adjust your diet and check again after a few days.

Ketone Urine Test Strips

A cheaper and less invasive way to find out whether you’re in ketosis is to check for ketones in your urine. These strips were also first developed for type 1 diabetics to find out if they were at risk for diabetic ketoacidosis. You can purchase urine test strips at many pharmacies and supermarkets, or via online shopping, at about 50-100 strips per pack for a much lower price than ketone blood strips, with an expiration date of 6 months.

It’s recommended to check urine ketone strips at the same time each day, like in the morning (this is also advice given for those who weigh themselves each day), or a few hours after your final meal of the day. This provides for a more accurate comparison. To check for ketones in your urine:

• Wash your hands, then collect a small sample of your urine.
• Put the absorptive side of the strip into the urine for several seconds before removing. 
• Wait as the strip changes color, then compare it with the ketone strips color chart that comes with your product’s packaging.
• Properly dispose of the test strip before washing your hands again.

The colors will reflect ketone concentration in your urine, with darker colors indicating high levels of concentration, and lighter colors signaling lower levels.

Ketone Breath Meters

The easiest and least invasive method of measuring ketones by far is the keto breath meter, but it is also the least accurate and not as sensitive as the other methods. Breath meters can run from $25-150 in price, and are even easier to use than urine strips.

• Turn on your ketone breath meter.
• Take a normal breath and blow as deeply into the meter as possible (a deep inhalation before exhaling can provide inaccurate results).
• When using it several times per day, take the highest reading as the highest ketone concentration in your breath.
• Let the device rest at least 3-5 minutes before using it again, otherwise the sensors may be overloaded.

Are Ketone Strips Accurate?

When it comes to accuracy, ketone strips far outperform the ketone breath meter. Ketone strips urine measurements are a better tool in the early weeks of a keto diet, because even though your body may be generating ketones, it is still adjusting to using them, so a lot of them will be eliminated in your waste (and exhaled via your breath, causing a fruity-smelling acetone-like scent).

However, once your body adapts to ketosis, it will use more ketones for fuel than it loses, and your urine may no longer test accurately for ketone bodies. On the one hand that’s great because it means you’re reaching ketosis! On the other hand, it may be harder to keep track of whether you’re about to get kicked out of ketosis too.

While the urine strips are more affordable, once you’ve been following a ketogenic diet for a few months, blood ketone test strips are going to be the most accurate way to understand your levels and if/how/when they fluctuate. Ultimately blood testing strips give you a long-term and true picture, though there is still the downside of elevated price and blood to draw. At the end of the day, it’s your decision to make.

Bottom Line: Do Ketone Strips Work?

Yes, they do work, though some work better than others. Ketone testing strips are far more accurate than breath testing devices, but while urine strips are more affordable and easier to use, blood testing strips are the the best testing device. 

If keeping a ketogenic diet is something you’re committed to, these tools will not be so necessary in the long run—you’ll be well-practiced enough to know what kinds of foods might kick you out of ketosis, and how to get back into it. However, for those beginning the journey to the state of ketosis, these testing strips work, and may help you reach your goals faster.