Ketosis is a state where a body breaks down fat for fuel, and the energy molecules produced from that process are called ketones. For anyone aiming to follow a keto diet—whether for health reasons or lifestyle changes—understanding ketones and the role of ketosis is crucial for making informed choices.
Let's break down everything from ketones to carb limits, signs that ketosis has kicked in, and the best ways to track your progress.
Jump to:
- What is ketosis?
- What are ketones?
- What do ketones do in your body?
- When does ketosis start?
- How long does it take to get into ketosis?
- 10 signs that you're in ketosis
- What are the benefits of ketosis?
- What are the dangers of ketones?
- How to test ketone levels in the body?
- What's the best way to test ketones at home?
- What’s the ideal ketone range for ketosis?
- Frequently asked questions
What is ketosis?
Our body typically relies upon carbohydrates as its primary energy source. When we consume food, the body breaks down the carbohydrates into glucose. This glucose is stored and transported to the cells by insulin to fuel our tissues and organs.
The consumption of carbohydrates, however, is intentionally decreased in a keto diet. As a result, when the body has no immediate carbs to produce energy, it uses an alternative fuel source: fat.
To turn fat into energy, the body goes through a metabolic shift. In this state, the liver breaks down stored fats into fatty acids and produces energy molecules known as ketones.
This entire process where the body predominantly uses ketones instead of glucose is known as ketosis.
Did you know? A keto diet isn’t the only way to stimulate ketosis. If your insulin levels are low, as seen in certain cases of diabetes, glucose can't effectively enter your cells. In response, the body begins producing ketones as an alternative energy source.
What are ketones?
Ketones are the molecular products made in the liver through a process called ketogenesis. They are produced from fatty acids when carbohydrates, the usual energy source, are scarce in the body.
It's important to note that the liver breaks down fatty acids into three main types of ketone bodies, specifically:
Based on the origin and the method of production, ketones can be categorized as:
- Endogenous ketones: Endogenous ketones are naturally produced by the body through ketogenesis during fasting, low-carb diets, keto diets, or low-insulin states.
- Exogenous ketones: Exogenous ketones are externally sourced ketone supplements, typically produced as ketone salts and ketone esters. They enable the body to achieve ketosis without strictly adhering to a ketogenic diet.
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What do ketones do in your body?
Ketones energize your brain and body in the absence of glucose, especially when carbohydrates are low, absent, or unusable. Here's a quick look at a few of their roles:
Provide energy for the brain
The brain typically relies on glucose for functioning as it can't directly use fatty acids. However, AcAcs and BHBs can cross the blood-brain barrier using monocarboxylate transporters (MCTs) and break down to produce adenosine triphosphate (ATP), the main energy currency of cells.
Fuel energy for cells
When glucose from carbs is unavailable, ketones step in to supply energy, especially to high-demand organs like the brain, heart, and muscles. Since they’re derived from fat, ketones provide a steady source of energy that can help maintain physical and mental performance
Help control appetite
Studies have found that the ketones in the body help suppress the secretion of the hunger hormone called ghrelin and feelings of hunger while increasing the release of satiety peptides (leptin), helping weight management efforts.
Reduced oxidative stress
When ketones are used for energy, they produce adenosine triphosphate (ATP), the cell’s energy currency, more efficiently than glucose. This process creates fewer reactive oxygen species (ROS), which are byproducts that can cause oxidative stress and cell damage, thus promoting healthier cells and possibly enhancing longevity.
When does ketosis start?
Ketosis is a natural metabolic process that occurs when your body switches from burning glucose to burning fat for energy. Your body can enter ketosis and produce more ketones under various conditions, such as:
How long does it take to get into ketosis?
If you eat only less than 50 grams of carbohydrates every day, it will typically take you around 2 to 4 days to enter ketosis.
When you start a low-carb or ketogenic diet, the body first depletes its glycogen stores within 24-48 hours. Once glycogen is exhausted, the liver starts producing ketones, which can be detected by the increase in ketone levels in the blood and urine.
By day 5, your body will enter a mild to moderate state of ketosis. However, it's important to note that full adaptation to ketosis—where the body efficiently burns fat and uses ketones as its primary fuel—may take several weeks.
The exact timing to get into ketosis varies widely from person to person, depending on factors like balanced diet patterns, age, carbohydrate intake, stress, activity level, and metabolic rate.
People often engage in physical activities and practice fasting to accelerate glycogen depletion and enter ketosis more quickly.
10 signs that you're in ketosis
So, you’ve started a low-carbohydrate diet but aren’t sure if you’ve entered ketosis? Look out for these 10 telltale signs:
1. Increased ketone levels
One of the most definitive signs of ketosis is the presence of ketones in your blood and urine. You can track ketone levels using a blood ketone meter or urine strips.
2. Keto breath
As your body produces ketones, particularly acetone, some of them are excreted through your breath, giving it a distinct, fruity, or acetone-like smell.
3. Weight loss
You can notice rapid weight loss during the first phases of ketosis, which is a combination of water loss (due to glycogen depletion) and fat burning. As you continue, fat loss becomes more apparent.
4. Increased energy and mental clarity
Many people report feeling more mentally clear and energetic once their body has adapted to ketosis. Since ketones provide a steady, reliable energy source for the brain, cognitive function can reportedly improve.
5. Decreased appetite
Ketones help reduce hunger by regulating hormones like ghrelin and leptin. This results in a natural reduction in appetite, which can help with weight management.
6. Digestive changes
You might experience changes in digestion, such as constipation or diarrhea, due to the change in your diet. These are usually temporary as your body adapts to using fat for fuel.
7. Increased thirst
Ketosis can lead to dehydration, particularly in the early stages, as glycogen (which binds water) is depleted. You may feel thirstier and need to drink more water than usual.
8. Improved physical performance
As your body becomes adapted to using fat for fuel, some people notice better stamina and endurance in physical activities, especially after a few weeks of being in ketosis.
9. Sleep disruptions
In the initial stages of ketosis, some people report trouble sleeping or feeling restless. This may be due to changes in hormone levels as your body adjusts to burning fat instead of carbs.
10. Keto flu symptoms
In the first few days of ketosis, many people experience what is known as the 'keto flu,' which includes symptoms like fatigue, headache, irritability, and nausea. These symptoms typically subside as your body adjusts to ketosis.
These signs can vary from person to person, and it’s important to remember that some may be temporary as your body adapts to the ketogenic state.
What are the benefits of ketosis?
The ketogenic diet garnered hype due to the several health benefits of ketosis, the most significant being weight loss. The process lowers your appetite, helping you feel less hungry and eat less food.
Besides that, it reportedly has other potential benefits for people suffering from:
Keto diet has been used as a treatment for epilepsy in children and adults who didn't respond to drug treatments. It helped prevent seizures and sometimes even caused remission.
Research has shown the keto diet may help improve neurological conditions, including neurodegenerative conditions like Alzheimer's disease and Parkinson's by providing the brain with a more stable and efficient fuel source.
Research suggests that ketones improve the function of vascular endothelial cells, which could help regulate blood pressure and lower cardiovascular disease risk factors. Also, its anti-inflammatory effects and the role of ketones as "rescue fuel" for the heart, help in cardiac disorders.
Research shows that a ketogenic diet can effectively lower blood sugar levels and reduce the need for insulin therapy in individuals with type 2 diabetes. It may benefit some individuals with type 1 diabetes also, though careful monitoring is essential to prevent complications.
What are the dangers of ketones?
Human bodies are made to handle both high-carb and high-fat diets. When you’re on a keto diet, your body balances blood sugar and ketone levels naturally. Most people just need to know if they’re in ketosis and over time, the levels tend to stabilize.
Having said that, people with diabetes, particularly type 1 diabetes, need to keep track of their ketone levels.
In this condition, the body makes little to no insulin because the immune system attacks and destroys the insulin-producing cells in the pancreas.
Without insulin, the body can’t use glucose (sugar) for energy, resulting in the production of ketones.
Normally, insulin helps balance the ketone levels, but here, without enough insulin, ketones can quickly build up to dangerously high levels, leading to a condition called diabetic ketoacidosis (DKA), where high levels of sugar(hyperglycemia) and ketones make the blood too acidic.
DKA can be life-threatening if not treated, so people with type 1 diabetes and also type 2 (for precaution) must monitor their ketone levels closely while looking out for these symptoms:
How to test ketone levels in the body?
You can get your ketone levels measured at a pharmacy or your home using various methods, including blood tests, urine tests, and breath analysis. Each method has its advantages, depending on your needs and how accurate you want the results to be.
Blood test
The most reliable way to measure ketones is through blood. You can do this at home with blood ketone meters, ideally 3 hours after eating your meal.
Simply, prick your fingertip with a lancet and drop blood on the testing strip. Once you insert the strip on the meter, it will show you your current ketone levels like with any blood glucose meter.
Note that the blood meters typically read the levels for beta-hydroxybutyrate bodies, the most prevalent ketone bodies in the blood.
Urine test
A simpler and painless way to check your ketones is with a dip-and-read urine test.
For this, dip a test strip into a urine sample. The strip measures acetoacetate, a type of ketone, and changes color based on its level. Once the strip changes color, compare it to the chart provided on the package. Generally, the darker the strip, the higher your ketone level.
Urine strips are affordable, but they’re less accurate than blood tests and may be unreliable if you’re dehydrated. Also, they don’t show your current ketone levels but rather reflect levels from a few hours ago.
Breath analysis
Another modern way to find the level of ketones in the body is using handheld breath analyzers.
These devices detect acetone, a type of ketone found in your breath, in parts per million (ppm). Levels ranging from 2–40 ppm, and sometimes even higher, may indicate you're in nutritional ketosis.
While reliable breath testing devices can be expensive and slightly less accurate than blood tests, they are painless and don’t require extra supplies like lancets or strips.
Having said that, people at risk for DKA should never rely on breathalyzers to check the levels of ketones.
Shop everything you need to measure ketone levels
What's the best way to test ketones at home?
The blood test is the most accurate method for measuring ketones, making it the best option for precise tracking, while urine tests are cheaper and easier, and breath analysis is convenient but less reliable.
What’s the ideal ketone range for ketosis?
The ideal ketone range for nutritional ketosis typically falls between 0.5 to 3.0 mmol/L of beta-hydroxybutyrate in the blood. This range indicates that your body is burning fat for fuel and producing ketones as a primary energy source.
To achieve optimal ketone range and maintain ketosis, you must restrict your carb intake to less than 50 grams of total carbs — or 25 grams of net carbs — per day through a planned ketogenic diet.
It's crucial to find an approach that aligns with your needs and is sustainable for long-term success. As always, consult with healthcare professionals or nutritionists for personalized guidance.
Disclaimer: This post contains affiliate links. If you purchase through these links, we may earn a small commission at no additional cost to you. Thank you for supporting us! This article is for informational purposes only and does not constitute medical advice. The information provided about ketosis, ketones, and the ketogenic diet is based on general knowledge and should not be used to diagnose, treat, or make health-related decisions. Before making any changes to your diet or lifestyle, consult with a qualified healthcare professional to ensure it aligns with your individual health needs.
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