The high-fat ketogenic diet is extremely hard to maintain. Eat just a few too many blueberries and you'll be knocked fat-burning mode. That's because restricting carbohydrates, your body's main fuel source, and protein forces your body to burn stored fat in a process called ketosis. As a result of this process, your body produces ketones.

Generally, 70 percent of your total calories will come from fat. Protein makes up about 20 percent, while 10 percent comes from carbs. Consuming large quantities of fat while limiting protein and carbs is challenging, and people often aren't truly in ketosis, says Registered Dietitian Melanie Boehmer of Lenox Hill Hospital.

"Sometimes people try and teeter into it and they won’t lower their carbohydrates enough," she previously told Men'sHealth.com.

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An easy way to determine whether you're actually doing keto the right way is by using an over-the-counter ketosis strip test.

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How do ketosis strips work?

There are two ways you can measuring ketones using strips: through urine or blood. Both are fairly simple to use. The urine tests are similar to pregnancy tests except they measure acetoacetate, a specific type of ketone, says Ashley Cuellar Gilmore, M.D., gastroenterologist and program director for IU Health Medical Weight Loss.

Typically, you'll dunk the strip into a cup of urine for a set amount of time. Strips are made with a type of paper that reacts to ketones by turning a different color, Women's Health reported. You'll then match the color on your stick to an accompanying color chart that offers an estimate of your level of ketosis. Usually, the darker the color the deeper you are into ketosis.

Cuellar Gilmore explained to Women's Health that urine levels are generally indicative of the levels found in blood. Blood ketones should measure 0.5 mM/dL at a minimum, but numbers between 1.5 to 3.0 mM/dL, are optimal, she said.

Blood keto strips are similar to urine except they require pricking your finger for a blood sample.

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Are ketosis strips accurate?

According to Gilmore, the strips aren't 100 percent reliable . Hydration can affect the concentration of ketones in your urine, which may give an incorrect reading. Although the urine strips aren't precise, they can give you an idea whether you're eating too many carbs. Blood ketone tests provide better results.

How to use ketosis strips

Test at the same time every day to get a baseline. This will help you compare progress, says health coach and keto expert Karissa Long. She recommends testing twice a day at different times.

“Morning and night testing is recommended because ketone levels are normally lower in the morning and higher at night so you can get an idea of your ketosis range throughout the day,” Long previously told Men's Health.

Ready to try them for yourself? Try these:

Perfect Keto: These earn high marks from more than 3,000 reviewers on Amazon. Bonus: a pack of 100 costs just under $8. (100 strips, $7.99 on Amazon)

Smackfat Ketone Strips: This popular kit comes with a color guide right on the bottle so you can easily read results. (100, $6.95 on Amazon)

Keto Mojo: These strips are more expensive and are better for people who aren't squeamish since they require a blood sample. (50, $49.50 on Amazon)

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Melissa Matthews
Health Writer
Melissa Matthews is the Health Writer at Men's Health, covering the latest in food, nutrition, and health.