How Long Does It Take to Get Into Ketosis? Important Facts You Need to Know

How long does it take to get into ketosis? To be honest, I hadn’t heard about ketosis until a few years ago. And I certainly wasn’t asking how long it would take me to get into ketosis! Now I’m glad that I did hear about it, and that I did get into ketosis, because it has made a significant difference to my health and my life.

If you’re still wondering what ketosis is and whether it’s important, I hope that I’ll be able to answer some of your questions. At the end, I’ll be asking you, "How long does it really, honestly, genuinely take to get into ketosis?"


What Is Ketosis?

Ketosis means that your body is producing ketones, and your brain is using the ketones as a source of fuel. Ketones are produced by the liver, as a product of breaking down fats.

what does mean Ketosis?

Ketosis is your body’s natural response to starvation. It is the reason humans have been able to survive through periods of shortage. What happens is that your body switches from using glucose as a fuel and uses your own stored body fat as fuel. (And some of us have ample stores!)

So that’s the answer to one of the first questions you may ask, "Is ketosis safe?" Yes, it’s safe, it’s how your body operates naturally. We’ve really messed with it, because we don’t go for long periods without food, so our bodies live off glucose all the time.

The ketosis that is bad for you is ketoacidosis, a life-threatening condition for Type 1 diabetics, when there are too many ketones in the blood together with high levels of glucose.

Your liver is always breaking down some fat, so there are always some ketones in your blood. But you are "in ketosis" when the level of ketones in the blood is between 0.5 mmol/dl and 5 mmol/dl. These are the levels given by Dr Stephen Finney who is a real expert in the field of ketosis. (If you are serious about finding out exactly how to take control of your weight and your health, Google "Dr Stephen Finney - ketosis". There are multiple videos that you can watch.)

Why Would You Want to Be in Ketosis?

There are really compelling health reasons for just about everyone to want to be in ketosis – you’ll learn about them if you watch some of the videos I recommended. But, for many, the main reason is to lose weight, and to achieve the health benefits that come from that.

Here are some outcomes of ketosis

Weight Loss

ketosis for weight loss

You will lose weight quite rapidly. The good news is that, although in the first week you may be losing stored water and carbohydrates, from then on you are losing fat. You will not be losing lean muscle mass, and your skin won’t become lose and flabby.

No Hunger Pangs

The reasons for this are quite complex and relate to the interaction of ghrelin, the so-called hunger-hormone, and leptin, the hormone switch that tells us when we’ve had enough and should stop eating. Both of these are usually faulty when we are overweight or obese, and both quite quickly come back to normal on a ketogenic diet.

More Energy and Focus

At the start, you might feel a bit sick, tired, have a bit of "brain fog" or headaches, as your body adjusts to the new energy source. People call this "low carb flu" or "keto flu". It passes in a few days, and your energy and focus levels will then improve considerably. It helps to take supplements, especially electrolytes, both because you are eliminating water, and also because you will be reducing salt as you change what you eat. You should supplement with sodium, potassium and magnesium every day.

Weight Loss From Exercise

Very high-performance athletes may have reduced performance at the start and they may need an adjusted ketogenic diet. For those of us who are just exercising at home or in the gym, the good news is that if you on a ketogenic diet, exercise will lead to significant weight loss. One study showed that those on a ketogenic diet lost 230% more fat than those on high carbohydrate diets.


what is the outcome of ketosis

You might have a bit of insomnia at the start, but you are likely to sleep much better once you have adjusted.

Digestive Issues

This may include constipation or diarrhea for a while until your body adjusts. Remember to add plenty of fibre, especially from green leafy vegetables, and to drink lots of water.

Bad Breath

Your breath might smell fruity or like nail polish remover. This is because one of the ketones is acetone, and it is excreted via your urine and breath. It will go away once your body adjusts.

So, if you’d like to lose some weight and gain some health, it might be a good idea to get into ketosis.

How to Get Into Ketosis

The way to induce ketosis is to force your body to switch from using glucose as fuel to using fat as fuel. You do this by changing what you are eating and how much you are eating. This is what is termed "nutritional ketosis".

You can do this in two ways:

The first is to cut back on carbohydrates in your diet. This includes sugars, starches, packaged and processed foods.

The second is to replace carbohydrates with proteins and fats.

How to get into ketosis?
  • There is a lot of debate about what type of fats are best, and we have talked about that in another article. Some fats that are particularly good are coconut and palm oil, because they are MCT (medium-chain triglycerides) oils, and they convert easily into ketones. You can get some ideas about high quality coconut oils here.
  • Good proteins are essential so that you don’t lose muscle mass instead of fat. This should be in moderate amounts – about a gram per kilogram of your lean body mass.

I was surprised, when I first started, at how little I actually knew about carbohydrates. Did you know, for example, that there are more carbohydrates in a medium-sized apple than in a slice of bread? So, be prepared to go on a learning journey.

Ketosis Cookbook
The Only Healthy Cookbook You Will Ever Need

What Are the Maximum Carbs Allowed for Ketosis?

You might ask how many carbs you should have to put your body into ketosis, and to stay in. There is no easy answer for that, because it depends on your size and your activity levels. It also depends on your health profile. So, for example, if you are obese and pre-diabetic or at risk of diabetes you may need to keep your carbs at less than 20 per day (as in the Atkins diet). If you’re an athlete you may need more, and at different timing intervals. For most people wanting to lose weight, the recommended carb limit is between 50 and 100 per day.

We’ll talk more about this in our article on vegetables for ketogenic diets.

The fastest way to get into ketosis is through fasting or protein-only days. Taking a supplement like berberine will also help. You can read about the really amazing benefits of berberine for weight loss here.

How to Tell if You're in Ketosis

It’s hard to separate the questions, "How do you know you’re in ketosis?" from "What are the benefits of ketosis?" and "What are the side effects of ketosis?" The answer to all of the questions is the same: There are significant changes to your metabolism when you switch to a ketosis diet, or, more accurately, a ketogenic diet. If you are experiencing any of the outcomes listed earlier, you are probably in ketosis.

At the start, you might experience some "side effects", but, in general, these go away as your body adapts, and the side effects then turn into benefits.

A definite sign is an increase in ketones in the blood. The best way to measure this is via a blood test. However, this requires special equipment. So, most people do a urine test, using a ketone stick or test strip. This is not as accurate but it is usually enough of a guide. A video below will explain how to read the results.

How Long Does It Take to Get Into Ketosis?

You have probably been running on a high-carb, glucose-driven fuel system for most of your life. It’s surprising how quickly your body will adjust to running on fat-as-fuel instead.

How long does it take to get into ketosis?

If you are running on glucose, insulin makes sure that some of it is stored as glycogen in your liver and in your muscles. If you don’t eat for a while, the body first turns to the glycogen for fuel. When the glycogen is used up, then the body looks for ketones, and this is when ketosis starts. It usually takes about 12 hours. You are likely to measure ketones in your urine within 2 to 3 days if you start with a fast or you have a few days of eating only protein.

However, you might not be in full "adapted mode" yet. You’ve got to stay in ketosis for long enough for your body to adapt completely. It will normally take from 4 to 6 weeks to get into full ketosis, or to be "keto-adapted".

Part of the explanation for the time taken, is that your muscles and your brain use ketones differently.

  • Muscles will use ketones for fuel when the levels in the blood are low - this is what is happening on your usual diet. When ketone levels are high, your muscles will use fat directly, without it first being converted to ketones.
  • Your brain uses ketones in proportion to what is in your blood.

So, when the levels of ketones remain high for long enough, muscles will use fat for fuel, and your brain will use ketones. When this happens, you are keto-adapted (and all those unwanted rolls of fat will literally be burning off you!). A below video, by Dr Stephen Finney, gives some idea of how you can maintain the levels and why it is important to do so.

So, How Long Does It Really, Honestly, Genuinely Take to Get Into Ketosis?

I’m afraid that only you can answer the question of how long it will take to get into ketosis. It will take until you decide to do something! There is sufficient information and science to give you help and guidance. But you must really want it and you must get started.

I hope that you will pick up on this challenge from me, and take the steps to get into ketosis and stay there. Your body will thank you for it.

Here are some related articles that you may want to read, and some products that might help you once you get started. Please let me know how you progress.

Ketosis Cookbook
The Only Healthy Cookbook You Will Ever Need

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