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How Long Does it Take to Get Into Ketosis? (+ How to Test for Ketones)

Louise Hendon | July 6
How to Test if youre in Ketosis Infographic #keto #article https://ketosummit.com/how-to-test-if-youre-in-ketosis

How long does it take to get into ketosis and how will you know for sure that your body is producing ketones?

This article will answer these questions and walk you through the best (and most affordable) ways to measure your ketone levels.

You can also check out this explanation for how long it takes to get into ketosis:

Before we start – What is ketosis?

Ketosis is broadly defined as having ketone levels of 0.5 to 3.0 mmol/L. You reach those levels when your body has switched from using mainly glucose as an energy source to using stored body fat and ketones (which it makes in the liver by breaking down your stored fat).

So now you know what ketosis is – the next step is how to get into ketosis.  You can reach a state of ketosis by altering your diet, reducing carbs to under 25 g per day while increasing the amount of fat you consume to make up the lack of carbs.  This is called nutritional ketosis.

How long to get into ketosis? Most people are in ketosis within 2-7 days of reducing carb intake below 25 g per day.  That said, there are ways to speed up the process, such as fasting or exercising in a fasted state.

Ketosis is a natural physical mechanism we all have that helps keep us alive during long gaps between meals, or when carbohydrates are drastically reduced from our diet.

Being in nutritional ketosis can help you feel more energetic, lose weight, focus more easily and improve your mood.


Dr. Andreas Eenfeldt, M.D. notes, “Ketosis results in a steady flow of fuel (ketones) to the brain, and you avoid big blood sugar swings. This often results in the experience of improved focus and concentration. Any brain fog will be long gone!”  He adds that weight loss, appetite control, and improved health markers are all potential benefits of Keto.

You can find out more about the benefits to your health by reading our Ketogenic 101 Guide.

Ketosis is NOT the same as Ketoacidosis

This is something which can cause a lot of folks confusion at first, and it’s important to know the difference.

  • Ketosis is beneficial for your health 
  • Ketoacidosis is harmful to your health

In ketoacidosis, your ketone levels are much higher: they’re greater than 3 mmol/L, combined with very high blood sugar. (1)

According to Registered Nurse Tammy Shifflett, RN, “[Diabetic ketoacidosis] can be life threatening condition for people with Type 1 diabetes and Certified Diabetes Educators spend many hours teaching preventive care for DKA.”

She adds, “This condition should not be confused with nutritional ketosis, the fat burning state reached when following the Ketogenic diet. The two conditions are quite different.”

For a non-diabetic, the body’s insulin will naturally keep ketone levels within a safe range.  So your nutritional ketosis won’t turn into ketoacidosis: your body has your ketone levels under control.


The folks who have to worry about ketoacidosis are primarily type 1 diabetics and also some type 2 diabetics and alcoholics – for the rest of us, it’s not something to be concerned about. (2)

Bottom Line:

Ketoacidosis is harmful for your health, while nutritional ketosis is good for your health.

3 Ways to Test if you’re in Ketosis

1 – Measure your levels with a Blood Ketone Meter

This is the most accurate way to measure your ketone levels, but it’s also the most expensive.

You prick your finger with a needle (just like you would with a blood glucose meter) and then put a drop of blood onto a test strip inserted into the ketone meter, which gives you a precise reading of your blood ketone levels.

The catch? Ketone meters are approx. $40 while the test strips are running $1-2 each…so over the course of a month, the cost of daily testing adds up!How to test if you're in ketosis

2 – Analyze your breath with a Breathalyzer

This is a cheaper and easier alternative, but your results could be skewed by alcohol consumption and how much water you drink.

You’ll have a reusable meter to use (which you charge with a USB cable) and to test your ketone levels you blow into it for 6-15 seconds.

Instead of measuring the ketones in your blood you’re measuring the level of ketones in your breath, and the two don’t always match up exactly. Blood ketone levels are usually a more accurate indicator of whether you’re in ketosis or not.

3 – Test yourself with Urine Ketone Strips

These are cheap, easy to use, and quick but they won’t work for everyone and can be inaccurate.

That’s because they measure the excess ketones your body excretes, instead of the actual levels of ketones inside your body – so if you’re in ketosis but your body is using up your ketones (which means you won’t have many in excess) then the strips might show an artificially low level of ketosis.

If you’ve just started on the keto diet, they’re a good way to tell if you’re making progress – your body will excrete most of the ketones you make in the beginning until it adapts to using ketones as fuel. That’s called becoming Keto-adapted and it usually takes 3-4 weeks.

For everyone else, they’re worth experimenting with at $10 for 50 strips, and you can always switch over to one of the other two methods if you find that they don’t work for you when you’re Keto-adapted.How to test if you're in ketosis

Other Signs you’re in Ketosis

There are a few other signs you can use to tell if you’re in ketosis, without using measuring devices:

    • Weight loss and reduced appetite
    • More mental clarity and increased ability to focus
    • Breath, sweat or urine which smells sweet or “fruity”

Bottom Line: You can test if you’re in ketosis by measuring your blood, using a breathalyzer, or testing your urine. There are other ways to tell if you’re in ketosis without using measuring devices. But testing your blood through a blood ketone meter is the most accurate.

What are Optimal Ketone Levels?

As you’ve probably noticed from the section on ketosis vs ketoacidosis, having higher ketone levels isn’t always better! But what are the ketone levels you should be aiming for?

What do the experts have to say?

We rounded up a few experts, like Dominic D’AgostinoDr. Thomas Seyfried, among others, and asked their advice. The main consensus is that ketone levels ranging from 0.5 to 3 mmol/L are a good range for Keto dieters to be in.

Dr. Tommy Wood, M.D., PhD notes that one size does not necessarily fit all when it comes to ketones. “There’s no such thing as an optimal recommendation for everyone because we just don’t know how to measure or understand all those processes as much as we’d like to think we do!”

If you’d like to do a deep dive into ketone level recommendations, we have full quotes from the experts in our article on Optimal Ketone Levels.

(Note: If you’re diabetic or you’re using keto to treat a disease, then your optimal levels will likely be different!)

Bottom Line: The experts agree that ketone levels from 0.5 to 3 mmol/L are the optimal.

How to test if you're in ketosis

Practical advice: Results matter more than Ketone Levels

If you were to forget everything else you’d read in this article, this is the one thing you need to remember:

Your results are more important than your ketone levels.

So if you’re on a ketogenic diet and you’re feeling more energetic, finding it easier to concentrate, and losing weight? Then you’re doing great, and there’s no need to worry if your ketone levels are lower than recommended.

Bottom Line: Don’t stress about measuring ketone levels. If you’re seeing results (weight loss, increased energy, etc), then you’re doing great!

You really don’t have to measure your ketone levels…

As we’ve said above – your results are more important than your ketone levels…

Los Angeles-based Nutritionist Angela Mavridis notes, “”The higher the number means you have more Ketones circulating in your bloodstream, but that does not mean that you are better at burning fat for fuel,”

She adds, “You will know once you are fat-adapted from hormonal signals, and not from higher Ketones on the blood meter.”

There’s a lot of different opinions on how to structure your Keto diet. Lots of folks recommend testing your ketone levels regularly. We don’t think Keto should take over your life – you don’t have to constantly be thinking about it.

That’s why we’ve designed Keto Meal Plans to make things easier for you. All the macros are already counted, the shopping lists are created, and we believe that if you eat these meals you can rest assured your ketone levels will be optimal for you (without having to prick your fingers and spending lots of money).

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Please pin the image below so that you and others can quickly and easily refer to the list and find out the best ways to tell if you’re in ketosis or not.

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Louise Hendon

Louise holds a Bachelors and Masters in Natural Sciences from Cambridge University (UK). She attended Columbia University for her JD and practiced law at Debevoise & Plimpton before co-founding Louise's Foods, Paleo Living Magazine, Nourishing Brands, & CoBionic. Louise has considerable research experience but enjoys creating products and articles that help move people just a little bit closer toward a healthy life they love. You can find her on Facebook or LinkedIn.