When following a ketogenic diet, measuring ketone levels in the body is an important part of maintaining a healthy level of ketosis. There are three types of ketones created in the body, and it’s helpful to know the different roles each type plays, both for monitoring their levels and for understanding the ketosis process.

In this article, we’re zeroing in on just one of those ketone bodies: acetoacetate. So, what is acetoacetate and how exactly does it fit into ketosis? To answer that question, let’s step back outside the aquarium (so-to-speak) and review what’s happening in ketosis.

What is Acetoacetate in Terms of the Ketogenic Diet

For most of us, the most common source of fuel for the body is glucose, because it is readily available when we eat foods containing carbohydrates, such as breads, pastas, sugars, fruits, or starches. When we digest carbs, they either turn immediately into glucose for the body to use or are stored as glycogen within our muscles, liver, and brain.

However, if there aren’t sufficient levels of carb intake, such as when someone is on a ketogenic diet (low carb, moderate protein, and high fat), the body will shift to break down fat for fuel instead. During this process, which is known as ketogenesis, ketones like acetoacetate are formed by the liver. The goal of those on the ketogenic diet it to rely on ketones as a primary fuel.

There are three main types of ketone bodies that can be detected in the bloodstream during ketosis.

What is Acetoacetate

The body creates acetoacetate first. Then, BHB is created from acetoacetate, and acetone is created spontaneously as a byproduct of acetoacetate. Acetoacetate is converted into BHB, which is the rich source of energy for the brain we care about. This process of converting fatty acids to ketone bodies is essential because the brain is not able to efficiently use fatty acids for fuel. Ketones, however, can cross the blood-brain barrier and carry energy.

The Function of Acetoacetate

Okay great, we now know that acetoacetate is the first ketone body produces in ketosis, but then what does it do? Why do we care? We care because acetoacetate will go on to generate Beta-hydroxybutyrate, which is the main energy shuttle in ketosis.

The ketones that are produced when fat is broken down, including acetoacetate, are important because when carbohydrates are restricted from the diet, ketone bodies can make up to 70% of the brain’s energy and up to 50% of the energy used for fueling the body’s tissues.

Both acetoacetate and BHB are full of energy, and their roles are to transport energy from the liver to other body tissues. For example, a lot of acetoacetate is converted to BHB, which will then shuttle energy to the brain. This is so important because normally fatty acids themselves can’t easily cross the blood-brain barrier to fuel the brain.

Typical Ketone Levels in Ketosis

When someone has a low carbohydrate intake or is fasting, they have blood ketone levels of between 0.5 millimoles of BHB per liter (mmol), which is considered mild ketosis, and 5 mmol, which is very deep ketosis.

The blood ketone concentration depends on how much carb and protein is consumed and how long the person has been eating a ketogenic diet. For most, blood ketone levels will rise above 1 mmol after eating keto for a few weeks. If you are eating what you think is “keto” but are not in ketosis, then what your diet is not “keto” and you need to adjust by further restricting carbs and protein.

Having ketones present in this range means the body is in ketosis and is burning fat for fuel, which has many benefits. Most people begin a ketogenic diet with weight loss as the goal, but that’s just the tip of the iceberg, and they stay for how it makes them feel. Benefits of ketosis can include:

  • Burning of body’s fat stores for energy
  • Less hunger, therefore less need to count calories
  • Steady blood sugar levels from little to no intake of refined carbs
  • Better results and less inflammation in those with acne
  • Improved triglyceride and cholesterol levels
  • Hormone regulation

Testing for Acetoacetate

To determine whether or not you’re in nutritional ketosis, it’s important to monitor the ketones present in your body. Thankfully, it’s fairly easy to detect acetoacetate.

When your body is in ketosis and ketone bodies are produced, excess ketones will “spill over” and excrete from the body in different ways. There are three main types of tests you can do for measuring ketone levels:

Acetoacetate is released from the body through the urine, so naturally, urine testing is the best method for measuring its levels. (BHB is released through the blood, and acetone is released on the breath.)

Urine testing can be done by peeing on a urine strip, which then changes color to indicate ketone level. These are very affordable to buy and can usually be purchased at your local pharmacy. There are certain companies that make urine strips specifically for testing ketones too.

Do keep in mind that sometimes urine strips aren’t a reliable method for measuring acetoacetate levels, especially if you’ve been in ketosis for a while. This is because the body becomes more efficient at using acetoacetate and turning it into Beta-hydroxybutyrate. Also, it’s impossible to maintain the variable of how hydrated you are across multiple tests. The more hydrated you are the more diluted your urine will be.

I have had numerous occasions where I pee on a strip and see no ketones and get bummed because I’m apparently not in ketosis. But then I do the gold standard blood test and sure enough, I have tons of ketones pumping through my body, they just aren’t in my urine.

The kidneys begin to adapt to the changes and become more efficient at reabsorbing acetoacetate, so over time you might not see as much of these ketones spilling over into the urine—even though they are indeed present in the body.

Plus, other factors can affect the results, such as your level of hydration and electrolytes in the body. But basically, if you’re sticking to your ketogenic diet yet seeing lower levels of ketones in your urine over time, it’s likely their production isn’t actually going down—your body is just using them more efficiently. When this happens, you might want to consider blood testing to monitor your levels of all ketones, especially BHB.

Is Acetoacetate Safe?

There are many common misconceptions surrounding ketosis and high ketone levels. Many medical professionals are taught that ketosis is harmful because it’s confused with diabetic ketoacidosis.

Diabetic ketoacidosis (DKA) is a dangerous condition that can occur in those with type 1 diabetes who have a lack of insulin, either from not making enough or not injecting enough.

DKA can also occur in alcoholics if they’ve been binge-drinking for a prolonged period of time without consuming carbohydrates. In ketoacidosis, ketone blood levels might rise above 10-25 mmol, lowering the pH level of the blood.

Ketosis vs. Ketoacidosis

It’s very important to note that DKA is not the same as nutritional ketosis that occurs as a result of a ketogenic diet, which is a safe and healthy way to benefit overall health, lose excess weight, and burn fat while maintaining sustained energy and steady blood sugar levels. And, as you can see now, acetoacetate plays a key role in this beneficial process.

Summary and Big Takeaways


  • Is the first step in the process where your body breaks down fat into ketone bodies.
  • Is important because it is the precursor to Beta-hydroxybutyrate, which is the main energy shuttle when we are in ketosis.
  • Can be tested with urine strips. However, the best way to test your ketogenic diet is by testing BHB levels in the blood.
  • Is safe.

Thanks for nerding out with us in the Perfect Keto Science Times and enjoy your day! 🙂



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Responses (1)

  1. Thanks for this article about hydration and urine testing. I have been bummed out because after very strict Keto diet the strips show that I am not in ketosis. I use electrolytes in my water to stay hydrated and drink a lot of water as I live in a very dry climate and hydration is important.
    Also informative about too much protein in the diet.
    Thanks again!

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