Ketosis is the natural metabolic state your body goes into when your liver breaks down fat for energy, thereby producing ketones. Ketosis can also be described as the state of having elevated ketone levels, typically above 0.5 millimole per liter (mmol/L). On a low-carb keto diet, ketones are the main energy source for the body. But how do you know when your body is in ketosis? Well, there are specific ketosis symptoms you can check for, or you can try out three different at-home ketone level tests.
Ketosis Symptoms: How to Tell if You’re in Ketosis
Bad breath is a not so pleasant but common symptom of ketosis. But don't worry... it's not really that bad. Plus, if you're used to drinking coffee, then bad breath probably isn't something new to you, right? :) Ketosis breath, or keto breath, occurs as a result of one of the three main ketones in the blood during ketosis called “acetone” leaving the body through the breath. While some people simply describe the smell of their breath as “bad,” others report a fruity smell. While bad breath may not be great news, it’s usually a sign you’ve reached that fat-burning stage of ketosis. This distinct smell can be managed by brushing your teeth throughout the day or chewing on a keto-approved, sugar-free gum.
While weight loss alone can’t be a surefire way to tell if you’re in ketosis, when seen in combination with other signs, it’s very likely you have elevated ketone levels. In fact, in the first week, it’s common to drop weight fast as you get rid of glycogen (carb) stores, which are responsible for water retention. Be sure to stay hydrated and supplement with electrolytes or bone broth during this stage to keep your fluid and electrolyte levels up. This can help you avoid common keto flu symptoms like muscle cramps, headaches, and fatigue. After the initial drop in water weight, your weight loss will steadily continue, but likely at a slower, more steady pace.
This can be one of the key components in helping people lose weight when on a keto diet. When your body is in a state of ketosis, it will typically reduce your appetite and food cravings, and according to research, this happens for a number of reasons. A high-fat, low carb diet helps lower ghrelin, your hunger hormone, reduce neuropeptide Y, an appetite-stimulator in your brain, and increase CCK, a peptide that creates the feeling of fullness. 
Initially when transitioning to the ketogenic diet, you may experience a decrease in energy as part of the keto flu, but after you get past the first few days, most keto dieters will experience increased energy and focus while in ketosis. [2, 3]
Like with your energy and attention span, your sleep patterns may also be negatively impacted when first trying to adjust your body to its new fat-burning state. You may experience difficulty sleeping or frequently wake up during the transitional keto flu (this usually only lasts a few days), but over time, low-carb diets have been shown to actually improve your sleep by increasing the percentage of deep sleep you get during the night compared to a more traditional carb-heavy diet.  So, as with most things in life, you may have to go through a few days of bad sleep, but on the other side of that, you should experience more restful and deep sleep. Hurray!
Ketosis helps shed water weight, which is a definite positive against bloating, but it can sometimes lead to increased thirst… and if unchecked, dehydration or electrolyte imbalance. So if you find yourself reaching for a glass of water more often than usual, you may be experiencing ketosis-induced thirst. Be sure to keep up with your water intake, and in order to help fight electrolyte loss, take a high-quality electrolyte supplement. If signs of dehydration persist, which is unusual, seek medical attention immediately.
Within the first couple of weeks of going keto, you may notice changes in digestion. Cutting out carbs can also mean cutting out fiber-rich foods if you're not intentional about it. So if you’re experiencing difficult bowel movements, be sure to check your fiber intake. Also take note of the amount of water you’re drinking to rule out dehydration as the culprit. However, digestive changes may not be a result of lacking certain essential components of a healthy diet; they also occur as your gut microbiome shifts according to your new diet.
How to Tell if You’re in Ketosis with Home Tests
You can tell a lot from ketosis symptoms, but if you really want to know if you're in ketosis, then you need to test your ketone levels. According to Volek and Phinney, who wrote "The Art and Science of Low Carb Living," the optimal range of ketones is 1.0–3.0 mmol.
The three methods of testing ketone levels are a urine test, blood test, or breath test. All of these tests can be performed at home very easily with the right tools. However, each one has its own set of pros and cons.
The most affordable option to measure your ketone levels is through a simple urine test using ketone test strips; however, they can also be a bit unreliable. But, if you are new to the keto diet or have a limited budget, this may still be the best method for you starting out. The ketone test strips will only change color if ketosis is reached.
Remember how acetone leaving the body through the mouth causes a bit of breath odor? Well, breath analyzers measure that same ketone as it leaves the body to determine whether you’re in ketosis or not. While breath tests seem to be fairly accurate, they’re not the best way to check your ketosis status.
While taking a blood test simply to measure ketone levels may not sound like the most appealing option, rest assured it’s only a simple prick… and as with the breath and urine tests, you can complete the blood test at home on your own with the use of a simple device. We personally recommend the brand Keto-Mojo. They make an affordable and reliable glucose and ketone meter kit.
All in all, you can have a pretty good idea of whether or not you’re in ketosis by the way your body feels and if any changes have occurred. However, if you want a more concrete measurement of ketone levels, we always recommend you test at home with one of the three different methods: a urine test, breath test, or, ideally, a blood test. The blood test is the most accurate, while a urine test is often the most affordable option... but can be unreliable.
Remember, your goal on the keto diet is to go from craving carbs to burning fat for fuel. The keto diet can provide you with a host of benefits, but it's going to take your body a bit of a transition to get into a steady state of nutritional ketosis. Like most great things in life, it's worth the work and temporary discomfort. And for some people, they don't even experience any of the negative symptoms. So who knows, you might be one of those lucky few. If you're not, don't worry. Push through it, and you'll be glad you did!