Ketosis is an alternative form of metabolism where your body uses ketone bodies as its primary energy source instead of glucose (sugar). Typically, ketosis kicks in when glucose is in short supply, such as during fasting, strenuous exercise, or a very low-carbohydrate diet.
In recent years, ketosis has been popularized by the ketogenic (keto) diet. However, recent research on the keto diet has shown that it may lead to weight loss and other benefits, which could explain its mainstream popularity.
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The Dangers of Ketosis
Ketosis is a normal metabolic process but can be dangerous under certain conditions. It typically occurs when your body doesn’t have enough glucose (for example, due to starvation or intense exercise). Your body then starts using ketone bodies made from stored fat.
Though ketosis offers benefits like weight loss and improved insulin sensitivity, it’s essential to consider its potential risks. For example, it can be risky for those with specific health conditions such as the following:
Exercise additional caution if you have type 1 diabetes or are on blood sugar-lowering medications. You may need to change your medication regimen or make dietary changes to avoid hypoglycemia.
Consult with your healthcare provider before starting a keto diet, especially for people with diabetes or pregnant or breastfeeding women.
Additionally, ketosis might lead to kidney stones, mainly if protein intake is excessive. Careful management of the fat-to-protein ratio is recommended to avoid such issues.
1. It May Cause Dehydration
Dehydration is a common early side effect of ketosis. Fortunately, it’s usually short-lived and treatable. You may experience dehydration early on while in ketosis because of changes in electrolytes that influence hydration. Research shows that the kidneys may excrete more sodium than usual from days two through six of ketosis.
Symptoms of dehydration caused by ketosis include:
To treat or prevent dehydration symptoms, drink plenty of water and other hydrating beverages while in ketosis.
Over-the-counter pain medications can also treat a headache when necessary.
2. It Can Cause Constipation
Some people experience constipation while in ketosis or following the keto diet. Ketosis may cause constipation and other digestive issues to arise due to the extreme nature of the diet changes.
The keto diet used to achieve ketosis requires you to eat very few grams of carbohydrates and, thus, fiber. Constipation may also be caused by simply eating fewer calories while on the keto diet.
Common symptoms of constipation include:
- Fewer than three bowel movements in one week
- Hard, dry, or lumpy stools
- Stools that are difficult or painful to pass
- Feeling like not all stool has passed after a bowel movement
To combat constipation while in ketosis, drink plenty of fluids and try to include fiber where possible. A fiber supplement may be helpful for some people, while others may need to use a laxative or enema to find relief.
Talk with your healthcare provider about how to safely use laxatives and enemas.
3. It Can Cause Electrolyte Imbalances
Extreme diet changes, such as those required on the keto diet, may cause electrolyte imbalances. They are typically seen early in ketosis (the first several days). An electrolyte imbalance may occur when the levels of one or more electrolytes are too low or too high.
Hyponatremia (low sodium) and hypomagnesemia (low magnesium) are common electrolyte imbalances in ketosis. Electrolyte imbalances may be due to dehydration, excretion of ketone bodies and electrolytes, and low micronutrient intake.
Electrolyte imbalance symptoms may include:
- Shortness of breath
- Fever
- Confusion
- Edema (swelling)
- Increased heart rate (tachycardia)
Electrolyte replacement beverages and supplements are typically consumed to treat low electrolyte levels. In the case of high electrolyte levels, certain medications or extra fluids may help.
Not everyone in ketosis will experience symptoms of an electrolyte imbalance. Your healthcare provider can provide further guidance.
4. It May Cause Keto Flu
Since becoming popular, the keto diet has been associated with something called the keto flu. It may occur in the first few weeks of starting the keto diet and reaching ketosis.
It’s often confused with other illnesses and may cause some people to stop the keto diet early on. Symptoms of the keto flu tend to vary but may mimic those of the flu.
According to one study, people who have experienced the keto flu reported:
- Headache
- Fatigue
- Nausea
- Dizziness
- Brain fog
- Upset stomach
- Muscle cramps and weakness
These and other keto flu symptoms should go away within four weeks as your body adjusts to ketosis.
Increasing your intake of water and electrolytes may help treat the keto flu.
If you get the keto flu, talking with a healthcare provider about ways to feel better is best.
5. It May Lower Your Blood Sugar Too Much
Some researchers believe the keto diet can help lower blood sugar levels, but it can also cause blood sugar to drop too low for some individuals.
Carbohydrates have the most direct effect on blood sugar levels. So, the very low carb intake during ketosis may lead to hypoglycemia (low blood sugar). Drops in blood sugar are of particular concern for people with diabetes.
In a small study, people with type 1 diabetes on the keto diet had an average of 6.3 episodes of low blood sugar per week, compared to one to two episodes per week on a less restrictive diet.
Symptoms of low blood sugar include the following:
- Feeling shaky or jittery
- Hunger
- Fatigue
- Dizziness
- Increased heart rate
- Headache
- Vision changes
Hypoglycemia may also be more likely in people who take blood sugar-lowering medications.
If you take such medications, talk with your healthcare provider about tapering diabetes medications to prevent low blood sugar before starting the keto diet.
6. It Can Cause Nutrient Deficiencies
Following either the keto diet or being in ketosis can lead to nutrient deficiencies due to the restriction of carbohydrates, which are vital sources of various vitamins and minerals. Potential nutrient deficiencies may include:
These deficiencies may lead to decreased cognitive function, respiratory infections, vision loss, bone loss, gastrointestinal problems, fatigue, and more. You may need to take a multivitamin or other supplements to avoid nutrient deficiencies in ketosis.
Talk with your healthcare provider for individualized guidance.
7. It May Cause Cardiovascular Risks
Research suggests that the keto diet may increase the risk of specific cardiovascular issues.
Though it can quickly lower triglycerides, blood pressure, and body weight, its long-term benefits for heart health remain unclear.
A review found that the keto diet correlated with higher total and low-density lipoprotein (LDL) cholesterol levels than diets with 45% to 65% carbohydrates. However, other studies in the review showed no significant differences in lipid profiles after three, six, or 12 months on the keto diet.
The potential risks are thought to be related to the high intake of animal-based products and saturated fats, which are linked to atherosclerosis and cardiovascular diseases.
To assess your cardiovascular risk, consider having a healthcare provider perform a lipid panel. Your risks may decrease after stopping the keto diet.
8. It May Cause Kidney Issues
Ketosis can negatively impact your kidneys, potentially leading to acute or chronic issues.
The keto diet has been associated with a higher risk of kidney stones, in part due to ketones making urine more acidic. Increased kidney stones may also result from people unintentionally eating more animal-based foods and protein than is recommended for this diet.
Signs of kidney stones include the following:
- Sharp pains in your back
- Blood in your urine (hematuria)
- Feeling like you need to urinate constantly
- Pain while urinating (dysuria)
- An inability to urinate (urinary retention)
- Cloudy or foul-smelling urine
For people with chronic kidney disease (CKD), ketosis may worsen conditions and increase the risk of complications like metabolic acidosis. If left untreated, metabolic acidosis may cause:
- Further decline in kidney function
- Muscle wasting
- Malnutrition
- Death
Consult a healthcare provider before starting a keto diet if you have CKD or other kidney problems to see if it’s safe for you.
What Causes Ketosis?
Ketosis occurs when your body uses ketone bodies for energy instead of carbohydrates. This can happen for several reasons:
- Low carbohydrates: When carbs are low, your liver converts fat into ketones, an alternate energy source. A very low-carb diet, like the ketogenic diet, causes ketosis by limiting carbs to under around 50 grams per day and increasing fat intake.
- Survival: Ketosis may occur during starvation, severe injuries, infections, or exhaustion.
- Medications: Some medications, such as SGLT2 inhibitors taken for type 2 diabetes, may also cause ketosis and have also led to diabetic ketoacidosis in some individuals.
Signs of ketosis include dehydration, constipation, and “keto flu.” Testing your blood or urine for ketones can usually confirm ketosis.
Ketosis vs. Ketoacidosis
Ketosis is a metabolic state in which the body uses ketone bodies for energy instead of carbohydrates.
Ketoacidosis is a severe condition in which ketone levels become dangerously high, making blood and urine too acidic. Ketoacidosis typically does not occur with ketosis. It typically occurs in diabetes, known as diabetic ketoacidosis (DKA). DKA is due to very low insulin levels and high blood sugar levels caused when glucose cannot enter cells.
Both ketosis and ketoacidosis involve high levels of ketones. However, ketoacidosis is life-threatening. Signs of ketoacidosis include the following:
- Rapid breathing
- Dehydration
- A flushed face
- Fruity-smelling breath
- Muscle stiffness or aches
- Nausea and vomiting
Seek immediate medical attention if you have signs of ketoacidosis. Delaying treatment may be dangerous.
Ketogenic Diet vs. Low Carb
Ketogenic diets and low-carbohydrate diets (LCD) differ primarily in their carbohydrate and protein limits. The keto diet tends to have a higher percentage of fat, lower protein, and half the carbohydrates of the LCD. Carbohydrate sources tend to be from non-starchy vegetables and small amounts of berries.
The following outlines the typical percentage and amount of carbohydrates, protein, and fat per day needed for a 2,000-calorie diet for each diet.
Keto diet (very low-carbohydrate):
- Carbohydrates account for about 5 to 10% of your total daily calories (around 40 to 50 grams).
- Protein is typically 10 to 20% of daily calories (50 to 100 g).
- Fat comprises 70 to 80% of daily calories (156 to 178 g).
Low carbohydrate diet:
- Carbohydrates comprise about 20% or less of your daily calorie intake (100 g).
- Protein may comprise 25% to 30% of daily calories (125 to 150 g).
- Fat constitutes 55% to 65% of daily calories (about 122 to 144 g).
| Macronutrient Breakdown for Specific Foods | |||
|---|---|---|---|
| Food | Carbs | Protein | Fat |
| Almonds, 1 ounce | 6 g | 6 g | 14 g |
| Avocado, half medium | 8.5 g | 2 g | 15 g |
| Cooked salmon, 3 ounces | 0 g | 20 g | 7 g |
| Whey protein, 30-g scoop | 2 g | 25 g | 1 g |
| Bread, 1 slice | 15 g | 3 g | 1 g |
| Blueberries, 1 cup | 21 g | 1 g | 0.5 g |
How to Reach Ketosis Safely
Ketosis is generally safe, but more research is necessary to understand its long-term effects and optimal methods for achieving it. To reach ketosis safely, it’s important to:
- Consult your healthcare provider: Get guidance from a healthcare professional or a registered dietitian nutritionist to develop a safe meal plan.
- Adjust your diet slowly: Slowly reduce your carbohydrate intake and increase your fat intake. Avoid making sudden changes.
- Monitor your progress: Track your state of ketosis with any tests and recommendations that your healthcare provider suggests.
This cautious approach may help ensure you safely reach and maintain ketosis.
Summary
Ketosis is when your body turns fat into ketone bodies to use as fuel. It does this when carbohydrates are too low to be used for energy efficiently.
Research regarding the safety of ketosis is ongoing. The ketogenic diet has made ketosis highly popular over recent years. However, there are many possible short- and long-term side effects of ketosis and the ketogenic diet.
Ketosis is not the same as ketoacidosis, a serious condition in which levels of ketone bodies become too high, resulting in acidic blood.
You should aim to reach ketosis safely. The best way to do this is by getting help from a healthcare provider, like a registered dietitian.
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