How to Tell If Your Body Is In Ketosis

It can be harder to enter ketosis than you might think, but there are telltale signs your keto diet is working.

By Alex Orlando
Dec 23, 2019 6:00 PMMay 16, 2024 8:28 PM
The word "KETO" spelled with food items on a grey background: "K" with fries, "E" with Brazil nuts, "T" with broccoli, and "O" with a half-boiled egg
Here's how to know if your body is in ketosis or not. (Credit: SewCream/Shutterstock)


Sign up for our email newsletter for the latest science news

The ketogenic diet — or keto, for short — is a high-fat, low-carb regimen that has been linked to a variety of health benefits, including weight loss and lower blood-sugar levels. The trendy diet, which eschews carbohydrates in favor of fats, works by triggering a metabolic state known as ketosis. 

During ketosis, as blood sugar levels plummet in the absence of carbs, fatty acids are broken down in the liver and converted into ketone bodies, another source of energy. Basically, during ketosis, cells burn excess fat, not sugar, to harness the energy the body needs to survive.

How Ketosis Feels 

For keto newbies, it can be hard to know whether or not ketosis is actually taking place — but a few common signs might help. At first, many dieters experience bad breath due a particular ketone, acetone, which is expelled from your urine and breath. And then there’s the famed keto flu, which refers to short-term symptoms like weakness and fatigue that occur as people transition away from carb-heavy fuels.

Read More: The Science Behind Fasting Diets

How To Tell if You’re in Ketosis

Other methods of identifying ketosis are a little more technical. The most accurate is to measure ketone levels in the bloodstream through commercially-available test kits. You can also find out your ketone levels with urine strips or a breath analyzer, but they’re not as reliable as blood monitors. However, if keto practitioners are following the diet, they should be activating ketosis.

Read More: Why Does the Keto Diet Cause Brain Fog?

How Long Does It Take To Get Into Ketosis?

A detailed review of multiple approaches to the keto diet shows that the speed at which you enter ketosis may vary depending on your starting strategy. Individuals who began the diet with a fasting period typically entered ketosis—where the body starts to burn fat for energy instead of carbohydrates—by the following day. 

Those who gradually transitioned into the diet generally reached ketosis in about two days. So, if you're considering starting a ketogenic diet and want to reach ketosis quickly, beginning with a fasting approach may be more effective than easing into the diet slowly.

Read More: How Do Low-Carb Diets Work for Weight Loss?

Is Ketosis Dangerous?

As your body transitions into ketosis, short-term symptoms typically subside within a few weeks. Staying hydrated and maintaining electrolytes can ease these effects. However, the diet’s restrictive nature could potentially lead to nutrient deficiencies and pose long-term risks.

For example, the high-fat, low-fiber nature of the diet can disrupt the delicate balance of the gut microbiome, which could lead to digestive issues. There's also an increased risk of kidney stones and heart health concerns.

Read More: Forget Dieting. Here’s What Really Works to Lose Weight

Article Sources

Our writers at use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:

1 free article left
Want More? Get unlimited access for as low as $1.99/month

Already a subscriber?

Register or Log In

1 free articleSubscribe
Discover Magazine Logo
Want more?

Keep reading for as low as $1.99!


Already a subscriber?

Register or Log In

More From Discover
Recommendations From Our Store
Shop Now
Stay Curious
Our List

Sign up for our weekly science updates.

To The Magazine

Save up to 40% off the cover price when you subscribe to Discover magazine.

Copyright © 2024 Kalmbach Media Co.