8 Serious Side Effects of Following a Keto Diet

Ketosis is a metabolic state in which the body uses ketones for energy instead of glucose, typically as a result of very low carbohydrate intake, such as on the keto diet. While ketosis is often associated with weight loss and blood sugar control, it can also cause a range of side effects..

1. 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:

• Dry mouth
• Headache
• Dizziness
• Visual disturbance

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. Constipation

Some people experience constipation while in ketosis 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.

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. 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:

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. 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 it.

If you get the keto flu, talking with a healthcare provider about ways to feel better is best.

5. Low Blood Sugar

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 to prevent low blood sugar before starting the keto diet.

6. 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:

• Thiamine
• Folate
• Vitamin A
• Vitamin E
• Vitamin B6
• Calcium
• Magnesium
• Iron
• Potassium
• Vitamin K
• Linolenic acid
• Vitamin B12

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 prevent nutrient deficiencies in ketosis.

Talk with your healthcare provider for individualized guidance.

7. Cardiovascular Risks

Research suggests that the keto diet may increase the risk of specific heart issues. Though the diet 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 heart 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. Kidney Issues

Ketosis can negatively impact your kidneys, potentially leading to short- or long-term 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.

Is Ketosis Dangerous?

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 and consult your healthcare provider if you:

• Have type 1 diabetes
• Are on blood-sugar lowering medication
• Are pregnant or breastfeeding

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.