How Long Does It Take To Get Into Ketosis?

When you start looking into the keto diet, you hear about the impressive weight loss that’s possible. You hear about the diet’s other health benefits, and you hear how drastically you’ll have to alter your eating habits.

You may also hear a lot about ketosis – even if you’re not quite sure what it means. (Don’t worry, many of the people who are on the diet don’t know exactly what it means either, even though they should.)

Ketosis is the key to the ketogenic diet; in fact, that’s how the diet got its name. Until your body enters the metabolic state known as ketosis, you’re not going to lose any weight. After you’ve achieved ketosis, though, that’s when the pounds usually start to disappear.

That leads to one key question: once you give up the carbs and drastically increase the fat in your diet, how long does it take to get into ketosis?

Unfortunately, answering the question is more difficult than asking it. It can take some people just a few days, it can take others a complete week, and for some it may be even longer.

To understand the full story and to make the most of your keto diet, you really should spend a few minutes learning what ketosis means and how it will affect your weight loss.

We can help with that.

The Basics of Ketosis

The reason a ketogenic diet works has to do with the way the body gets its energy.

When we’re eating normally, the body converts the carbs we eat into glucose, a form of sugar. It uses that glucose to power the metabolism, and any glucose that’s left over is stored in the liver and muscles, in a form known as glycogen.

If there are no carbs to convert, the body has to look elsewhere for an energy source. It starts by burning glycogen. Once the stored glycogen has been used up, however, the body gets its energy from molecules known as ketones – which are produced when the body burns fat that’s stored elsewhere in the body. When the body is using ketones instead of glucose for energy, it’s said to be in “ketosis.”

That explains the reason that you have to stop eating almost all carbs on the keto diet. The lack of carbs deprives the body of glucose, and forces the body into ketosis. It also explains why you lose weight on keto: the body is burning your fat stores to get the energy it needs.

Now that you know more about ketosis than most of the people who are on the diet – the question remains: how long does it take to get there?

Entering Ketosis

Let’s start with the initial phase of keto, when the body has been deprived of carbs for fuel and begins burning glycogen instead. If you’ve previously been eating a lot of carbs, you have more glycogen stored up than someone who’s already been on a low-carb diet. In that first case (previously eating lots of carbs), it’s understandably going to take the body a while to use all of its stored glycogen, before it needs ketones and goes into ketosis to get them.

So that’s one reason why some people go into ketosis faster than others; the more carbs they’re accustomed to eating, the longer it will take.

If you exercise regularly or have a naturally high metabolism, you use up energy pretty quickly. Once you stop eating lots of carbs your body still needs lots of energy, though, and it won’t be long before it’s burned through its stored glycogen. So it will enter ketosis pretty quickly to get the ketones it requires to keep going.

In other words, the more active you are, the more likely you are to go into ketosis quickly after you start the keto diet.

Other factors can come into play as well, such as your age (which affects your metabolism) and how rigorous a keto diet you choose to follow. According to Diet Hive, the optimal mix of micronutrients is 75% fat, 20% protein and 5% carbs. However, if you choose a version of keto that allows 10% carbs, it will take you longer to get into ketosis. Conversely, if you start your keto diet with intermittent fasting (as some suggest), you may get there faster.

Entering Ketosis: What’s Slow, and What’s Fast?

If you’re eating 20 grams of fat per day (that’s around 5% of most people’s normal caloric intake), it should take between 1-4 days to enter ketosis, unless you’re also dealing with one of the other factors we’ve mentioned (like previously eating lots of carbs or having a slow metabolism). In that case, it can take as long as a week.

Some versions of keto allow you to eat as much as 50 grams of fat per day, and in that case, it can take as long as 10-14 days to enter ketosis.

One important thing to note: Just because you’re in ketosis, that doesn’t mean that your body fat will start disappearing the same day. You may lose some water weight initially, but until your body “fat-adapts” it won’t be running completely on ketones. That can take several weeks.

And until your body is fully adapted and using only ketones as fuel, you will probably go through what’s commonly called the “keto flu.” Its symptoms include fatigue, muscle cramps, headache, nausea and vomiting. It’s not really the flu; it’s just your body losing water, potassium and sodium, and it only lasts a week or so at most. It’s also a sign that you’re in the early stages of ketosis.

After that, you should feel more energized, more clear-headed – and the weight should start vanishing just as you hoped when you started the diet.

How Do You Know If You’re in Ketosis?

Ketones may seem mysterious, but they can easily be detected in your blood or urine.

The best way to check to see if your body is producing elevated levels of ketones is with a blood test. You don’t need to see your doctor; there are at-home ketone meters you can buy. Ketone levels (called BHB) above 0.5 mmol/L (millimoles per liter) means ketosis is starting. To stay in ketosis, they should be above 1.5 mmol/L.

You can also use a breath meter which measures the amount of acetone (one type of ketone) in your breath, or test strips which display different colors based on the amount of ketones in your urine. The breath meter is more accurate than the test strips, but they can each give you a decent idea of whether you’re in ketosis.

Getting impatient? You can often kick-start ketosis with the intermittent fasting we’ve mentioned earlier. You can also consume either a tablespoon of MCT oil (which goes straight to the liver to be converted to ketones) or synthetic ketone salts and esters (known as exogenous ketones).

One final question some may have: if you cheat and fall out of ketosis, how long will it take to get rolling again after resuming your keto diet? It depends on how long you’ve been on keto and how badly you’ve cheated but it generally takes 1-3 days, and intermittent fasting, MCT oil or exogenous ketones may help speed things up.