Nutrition

How to Detect Ketosis

State of ketosis, what's keto breath & how to read ketone strips.

How can you tell if your low-carb dieting efforts have been effective enough to induce a state of ketosis? Learn how to detect ketosis and check your ketones. 

This article is aimed at readers who’ve already done some research into ketogenic diets. A ketogenic diet is an extremely low-carb and high-fat diet, which has some potential side effects. Should you want to learn more about the ketogenic diet and understand the pros and cons, we recommend you read this article.

ketogenic diet consists of 70-75% fat, 20-25% protein, and 5-10% carbs. For an average person who requires 2,000 calories per day, that equates to a maximum of 50 grams of carbs per day. The average American woman eats more than 4 times as much (around 224 grams carbs per day).

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Restricting carbs means less glucose

The body of a healthy person who gets their nutrition from a balanced ratio of macronutrients — protein, carbs and fat — burns glucose as their main source of energy. Glucose typically comes from carbohydrate-based foods (like bread, pasta, fruit, legumes, whole grains, soda, etc.).  Those are used to provide the body with energy or stored in the form of glycogen in the muscles and liver. When calories or carbs are reduced strictly, there isn’t enough glucose available to the body. As such, it seeks an alternative strategy in order to meet the body’s energy demands and to keep functioning properly.

The state of ketosis: Finding an alternative source of energy

The state of ketosis means that the body has switched from depending on carbohydrates for energy to burning fats for fuel. This means not only dietary fats (olive oil, guacamole, deep-fried pig ears) but also body fat — clearly a desirable state for anyone looking to shed extra weight.

When the body metabolizes fat, it generates molecules called ketones (also known as ketone bodies). As you restrict carbohydrate intake and amp up the dietary fat, more fat is metabolized and a greater quantity of ketones are created. Most of the cells in your body — including those in your brain — are able to use ketones for energy, although many people experience an adjustment period (1-3 days) often called the low-carb flu.

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For healthy individuals, ketosis usually kicks in after 3 to 4 days of eating less than 50 grams carbs per day. Ketosis can also happen after a very long exercise session, during pregnancy or for people with uncontrolled diabetes.

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Note: For a person on a 2,000 calorie ketogenic diet, carb intake should not exceed 50 grams, but the general recommendation is somewhere between 20 and 30 grams. In the infographic above, the macronutrient and meal recommendations are based off a carb total of 5-10% of a 1600kcal diet, amounting to 20-40 grams of carbohydrates per day. 

How to detect ketosis

Following a very low-carb diet, with less than 50 grams carbs per day, does not necessarily mean your body switches to ketosis. For instance, exercising or eating too much protein can kick you out of ketosis. There are different methods to find out if your body has switched to ketosis.

#1 Keto breath

Acetone is one of the three attributes of ketone bodies produced as a by-product when fatty acids are broken down for energy in the liver and kidneys. As a result of the released acetone, the smell of the breath changes when entering ketosis. It can be described as “fruity” or even “metallic” – it’s been likened to overripe apples.

If you notice this happening in your first few days of changing your diet, it could mean you’ve entered ketosis. Brushing, flossing or scraping the tongue doesn’t help to kill the bad breath, but it usually diminishes after the first few weeks.

Acetone can also be detected by using a Ketonix device, which measures the acetate/acetone concentration in the breath. Those devices are rather expensive and not always very accurate.

#2 Increased thirst and dry mouth

When shifting to a ketogenic state, thirst typically increases. The body uses up excess glycogen and increases the need for urination. Checking how thirsty you are is very inaccurate if you want to find out if you’re in ketosis.

As insulin levels decrease while following a ketogenic diet, the body starts expelling excess sodium and water. To balance electrolytes, it’s recommended to add 2-4 grams of sodium per day to your diet when following an extremely low-carb plan.

#3 Detecting ketones in urine

A more accurate way to check for ketosis is to use ketone urine testing strips, often referred to by the brand name Ketostix. The strips are inexpensive and help to check ketone levels quickly. If you’re in ketosis, the strip will change its color. The strips usually come with a guide to find out how “deep” the level of ketosis is.

Pass the test end of the small paper keto strip directly through your urine stream (alternatively, collect urine in a clean, dry container and dip the strip in afterward). Shake off any excess, then wait 15 seconds. The Ketostix color meaning is on a tonal spectrum that will show you what state of ketosis you’re in. Here is a short breakdown on how to read ketone strips:

  • If the keto strip changes color from its original beige — compare the color to the guide on the side of the bottle to find out how “deep” your level of ketosis is.
  • Deeper purple levels generally indicate higher levels of ketones. This doesn’t mean deep levels are a desirable state though. A low-to-mid level is often linked a better overall well-being.

Keep in mind that the ketone levels in the urine don’t necessarily match with ketone levels in the blood. For instance, the concentration of ketones in the urine changes depending on how hydrated you are. Dehydration may result in a false positive. This is likely to happen when testing ketone levels in the morning. On the other hand, drinking lots of water can result in a lower concentration of ketones, meaning a false negative.

Ketone strips color chart

This Ketostix color chart will help you assess whether you’ve reached ketosis, and if so to what extent. Make sure to wait precisely 15 seconds after the test strip comes into contact with the urine and compare the color of the test area to that of the corresponding spectrum below.

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#4 Blood tests

Blood tests are the most accurate (and the most expensive) way to measure if your body has switched to ketosis. Blood ketone testing is typically used by people with diabetes. To test ketone levels, you need a blood ketone meter and a kit that includes a lancet pen and ketone test strips. Don’t confuse ketone test strips with glucose test strips as the latter won’t test for ketones.

The body is typically in ketosis when the blood ketone meter measures between 0.5 and 3 mml/L.

Potential errors from testing for ketones in urine

Ketone levels in the urine don’t necessarily match ketone levels in the blood. There are a couple reasons why this might be the case.

How hydrated you are can make a big difference regarding the concentration of ketones in your urine. Dehydration may result in a false positive, which some folks find happens every morning to a mild degree. Likewise, drinking a ton of fluids — and you should be drinking water like it’s your job — will result in a lower concentration of ketones, meaning a false negative.

As time goes on, people following ketogenic diets tend to measure lower levels of ketones in their urine despite still being solidly in fat burning mode. At this point, a blood test may be necessary to accurately test for ketosis — but these are significantly more expensive (plus, you have to prick your finger instead of simply urinate). If you’ve been following good eating habits and have been consistently in ketosis for the weeks following, there’s likely no need to fret over it.

Keto diets don’t always result in weight loss

Keep in mind that you do require fewer carbs if you maintain a non-stressful and sedentary lifestyle. However, it’s different if you work out regularly or have a demanding job. Carbs help the brain, the heart and the nervous system to function properly. It’s not necessary to cut carbs short in order burn fat.

The bottom line

  • Before switching to a keto diet, make sure to do further research. It’s not necessary to drastically reduce carbs in order to lose fat.
  • Being in ketosis generates elevated levels of ketones, which are detectable in the breath, urine, and blood.
  • Ketone urine testing strips (like Ketostix) are the quickest, easiest way to test for ketones in urine.
  • Hydration and amount of time spent in ketosis may affect Ketostix (urine test strip) results.
  • Ways of how to check your ketones include ketone urine testing strips, blood tests, increased thirst or a change of your breath smell also known as keto breath.