Executive Summary
Ketosis is a safe body mechanism whereas ketoacidosis is a life-threatening emergency. The key difference is the level of ketone buildup in the blood. Ketosis involves a moderate level of ketones produced when the body uses fats for energy, while ketoacidosis refers to a dangerously high level of ketones.
Ketosis has mild symptoms like fatigue, bad breath and decreased appetite. Ketoacidosis involves severe symptoms such as fruity-smelling breath, excessive thirst, frequent urination, nausea and vomiting, confusion and disorientation, and rapid breathing.
The most reliable way to distinguish between ketosis and ketoacidosis is the blood ketone test, which measures ketone levels in the blood. Home-administered urine ketone tests and blood ketone meters can help monitor ketone levels, too.
Ketosis is a harmless metabolic process whereas ketoacidosis is a life-threatening emergency. Both involve increased blood levels of compounds called ketones. So it is vital to understand the differences.
What are Ketones?
Ketones are chemical compounds with acetone-like structures. They have sweet, fruity smell, closely resembling that of nail-polish remover or paint thinner.
Ketogenesis
Your liver is continuously breaking down fats into ketones and pushing them into the blood. Your body cells can use such ketones as fuel for generating energy. However, when you have enough blood glucose, ketones are not needed as an energy source and the body maintains their levels low, around 1 mg/dL. At these insignificant levels, ketones are not excreted in the urine.
When the blood glucose is low, blood insulin levels drop. This triggers fat cells to release more free fatty acids. When the blood has a lot of free fatty acids and very little insulin, the liver goes into overdrive, converting free fatty acids into copious amounts of ketones. Ketones may now appear in the urine.
Ketosis
If one undergoes starvation, fasting (longer than 12 hours), very-low carbohydrate diet (ketogenic diet) or prolonged-exercise (such as marathon running), the blood glucose is depleted and the liver makes and pushes more ketones into the blood.
When the blood ketone levels rise above 1 mg/dL, the body is said to be in the state of ketosis. The body cells burn ketones to fulfil a part of their energy needs. This process generates acetone as a byproduct, which is expelled from the lungs along with carbon dioxide. Your breath acquires acetone’s fruity smell and is called ‘keto breath’.
If ketone levels are between from 1 mg/dL to 3 mg/dL, it is considered light ketosis.
Ketosis in Running
Your body has enough glucose reserves to last about 30–32 km of running. When these stores are nearly over, the body shifts to ketones for energy. This causes a sudden drop in running speed, a phenomenon known as ‘hitting the Wall’ in the running world. Untrained runners often encounter this stage when attempting marathon distances.
If ketone levels climb above 3 mg/dL, the ketosis is strong and a runner can feel ‘acetone on his breath’.
Ketosis for Weight Loss
Ketosis is used as a weight loss strategy since it involves utilising fats as fuel. However, weight loss needs a strong ketosis, with ketone levels between 3 mg/dL and 6 mg/dL.
A kilogram of ‘fat’ has 9,000 calories, while a kilogram of ‘body fat’ has only 7,700 calories because your body stores proteins and water with fat. Our bodies need 2,000 to 2,500 calories a day. So you would expect that by starving yourself for 4 days, you can lose a kilogram of fat.
However, after a 12-hour fast, only 2–6% of your body’s fuel needs are covered by ketones, which rise to 30–40% after a 3-day fast. You need at least 3 days of fasting to enter the strong-ketosis stage, and probably go without food for 8 days to lose a kilogram of fat.
The quick weight loss in first couple of days of fasting is lost water. Every gram of glucose (or rather, glycogen – the primary source of glucose stored in the body) is bound to 3 grams of water. As glucose is used, water is released and excreted through sweat or urine.
When ketone levels climb even higher, things turn problematic.
Ketoacidosis
As ketone levels rise above 6 mg/dL, the blood pH starts becoming less alkaline (and more acidic). The body loses its ability to regulate ketone production. This is a medical emergency called ketoacidosis.
When ketosis does not turn into ketoacidosis
Normally, ketosis does not end up in ketoacidosis. The ketones generated by the liver stimulate the pancreas to produce a little bit of insulin. In ketosis, this insulin stops your fat cells from releasing too many free fatty acids into the blood. In turn, the liver’s fat-to-ketone conversion is kept in control, never allowing ketone levels to exceed 5-6 mg/dL.
However, if insulin levels are too low, this regulation falls apart.
When ketosis turns into ketoacidosis
There are various situations in which the blood insulin levels may become very low.
Starvation ketoacidosis
If one does not eat for many days, the body switches to fats for energy. When the body’s fat stores run low, the body starts to break down muscles and their proteins are released as amino acids into the blood. At this starvation stage, there is a chance of ketosis ending in ketoacidosis as the insulin levels are very low. This is called starvation ketoacidosis.
In many religions, fasts are observed for days and even weeks. People take them as a proof that ketosis cannot turn into ketoacidosis. However, there are reported cases of fasting-related ketosis turning into ketoacidosis in lean individuals.
Actionable Tip: If you have very little body fat, you should keep an eye for starvation ketoacidosis.
Alcoholic ketoacidosis
An alcoholic person may drink extensively. One gram of alcohol provides 7 calories and a drunkard may not feel the need for food for a few days. However, his blood glucose can dip perilously low in those days, triggering excess ketone production.
Alcohol prevents the liver from producing glucose from glycogen (carbs), amino acids (proteins) and glycerol (fats). It also reduces insulin secretion and burning of fats for energy. The ketone levels shoot up causing alcoholic ketoacidosis.
Actionable Tip: If anyone does not eat for 2-3 days after an alcohol binge, observe him for signs of alcoholic ketoacidosis (search online).
In some situations, the blood glucose levels may be normal or high; yet, you may get excess ketone production, leading to ketoacidosis.
The science is still unclear (at least, to me); but it seems that for ketoacidosis, there is no restriction on blood glucose levels but blood insulin needs to be very low. This can commonly happen in diabetes.
Diabetic ketoacidosis
Diabetics are vulnerable to developing ketoacidosis as many, though not all, suffer from insulin deficiency.
In type 1 diabetes, the pancreas cannot produce insulin and the person needs to take insulin injections regularly. If type 1 diabetes is undiagnosed, untreated or the patient misses an insulin injection, his body can be in insulin deficiency.
In the very late stages of type 2 diabetes, the pancreas has exhausted its insulin-producing ability and the patient has to rely on external insulin.
In either of these situations, blood insulin levels can be very low and the body may not able to utilise blood glucose. Scarce insulin causes fat cells to release free fatty acids in large quantities. The liver makes more ketones but the body cannot utilise all of them and their levels keep rising dangerously.
The blood has abundant glucose; yet, the ketones are formed in copious amounts. This is called diabetic ketoacidosis.
Gestational diabetes is a temporary form of diabetes in the third trimester of pregnancy, during which a pregnant woman can be vulnerable to diabetic ketoacidosis.
Actionable Tip: Do not miss your insulin shot. If you have diabetes, you should remember the signs of ketoacidosis, which include fruity-smelling breath, excessive thirst, frequent urination, nausea and vomiting, disorientation or confusion and very high blood glucose. Read on this website: Diabetic Ketoacidosis: What Every Diabetic Should Know.
Thus, non-diabetic ketoacidosis develops with low insulin caused by low blood glucose, whereas diabetic ketoacidosis can happen with low insulin without restriction on blood glucose levels.
Interestingly, you do not need to have diabetes to get diabetic ketoacidosis; the name refers to a typical scenario that is observed in diabetes: high blood glucose but no blood insulin.
If a normal person somehow ends up with low insulin and high blood glucose, he will get diabetic ketoacidosis. For example, acute stress can precipitate this.
Stress ketoacidosis
Any event that is stressful for your body increases the release of stress hormones, which reduce insulin secretion. They make the body cells resistant to insulin action, a condition called insulin resistance. Effectively, your body acts as if there is very little insulin present, increasing the risk of diabetic ketoacidosis.
Stress need not be of mental kind. If a person develops an infection, it is stressful on the body. Thirty percent of the diabetic ketoacidosis cases are due to an infection.
A major accident, injury, or a major surgery can be traumatic and stressful to the body and may lead to diabetic ketoacidosis. Such situations are best monitored by medical professionals.
Ketogenic Diet
The proponents and detractors of keto diets have extreme positions about their safety for ketoacidosis. The truth lies somewhere in between.
Since there is a thin line (blood ketones ≈ 6 mg/dL) between ketosis and ketoacidosis, a ketogenic diet should be followed carefully. Three rules of thumb:
- If you are a diabetic, follow a ketogenic diet only under expert supervision.
- Remember the signs and symptoms of ketoacidosis and at the first hint, inform people around you and seek medical assistance.
- This will need you to be more conversant about how the body functions, but always think: “Can this be reducing my blood insulin levels below normal levels?” If yes, stay alert.
To Read More
- Cleveland Clinic: Ketosis
- MedicalNewsToday: Differences between ketosis and ketoacidosis
- Diabetes.co.uk: Nutritional ketosis vs diabetic ketoacidosis (DKA)
- UCLA Health: Ketosis, ketoacidosis sound similar, but not the same thing
- Healthline: Ketosis vs. Ketoacidosis: What You Should Know
- Zoe: What’s the difference between ketosis and ketoacidosis?
- Wikipedia: Ketone Bodies
- MSD Manual: Alcoholic Ketoacidosis
- Cedars-Sinai: Diabetic Ketoacidosis
First published on: 23rd January 2025
Image credit: mdjaff on Freepik
Last updated on: 24th January 2025