Potential Risks to Know Before Trying the Ketogenic Diet

The ketogenic diet offers immense benefits for weight loss, blood sugar control, brain health, and disease prevention when followed correctly. 

However, drastically reducing carb intake is a massive metabolic shift that comes with potential downsides if not properly implemented. 

Like any restrictive diet, keto is not right for everyone. Understanding the associated risks enables individuals to make an informed decision if keto aligns with their health goals and to follow it in a sustainable, healthy manner. 

This article explores possible concerns like the “keto flu”, nutrient deficiencies, hypoglycemia, constipation, kidney stress, and more. 

Weigh the pros and cons and work with a functional medicine practitioner when adopting a ketogenic diet. 

Potential Risks to Know Before Trying the Ketogenic Diet

The “Keto Flu”

When initially transitioning into ketosis, carb withdrawal manifests in symptoms known as the “keto flu.” Headaches, dizziness, fatigue, irritability, nausea, constipation, cramps, poor exercise performance, and brain fog are common as your body adapts from using glucose to ketones and fats for fuel. 

This lasts anywhere from a few days to a few weeks as your metabolism shifts gears. While uncomfortable, it’s a normal adaptation process. Staying hydrated, getting enough sodium, eating more fat, and resting will help counter symptoms until they pass. 

Nutrient Deficiencies   

A poorly planned keto diet high in processed foods risks certain nutrient deficiencies. Without adequate fruits, vegetables, legumes, and whole grains, one may become deficient in vitamin C, magnesium, iron, folate, fiber, and antioxidants. 

The diuretic effect of lowered insulin can also result in sodium, potassium and magnesium depletion if intake is not increased. 

Supplementing with a multivitamin, magnesium, potassium and sodiumgluconate and emphasizing low-carb produce can prevent this. Annual bloodwork assessing micronutrient status is recommended.


In non-diabetics, very low carb intake can occasionally trigger reactive hypoglycemia, a condition where blood sugar crashes, causing shakiness, heart palpitations, sweating, and anxiety that subsides upon eating carbs. 

Some individuals are carb intolerant due to metabolic disorders. Consulting with a functional medicine practitioner helps uncover potential blood sugar regulation issues and customized carb intakes and supplements that prevent hypoglycemia while supporting ketosis. 


Drastically reduced fiber from grains and certain veggies may cause constipation, an uncomfortable side effect of keto. 

Staying hydrated, adding coconut oil or MCTs to drinks, taking magnesium, eating plenty of low-carb veggies, and possibly psyllium husk can relieve this. 

Move bowels promptly when the urge arises. Working with a nutritionist ensures balanced nutrient intake.   

High Cholesterol

Keto shifts LDL particles to lower risk large, fluffy LDL but in certain individuals, it may raise overall total cholesterol and LDL on blood tests. 

Get tested 3-6 months into keto and annually. If numbers are very elevated, adjust fat macros, exercise more, increase fiber, and improve diet quality. 

Discuss medication if needed. LDL should lower after adaptation.

Kidney Strain 

In those with healthy kidneys, keto does not damage them despite higher protein. However, those with chronic kidney disease require close medical supervision, limited protein, and higher carbs. 

The diuretic effect of keto also alters hydration and electrolytes which strains kidneys if intake is inadequate. Drink sufficient fluids and balance electrolytes. 

Avoid keto if you have kidney disease without a doctor's oversight.


When adhered to short-term or in an unbalanced manner, the keto diet does pose certain risks like hypoglycemia, constipation, nutrient deficiency, kidney strain, high cholesterol, and side effects during adaptation. 

However, with proper precautions, medical oversight if needed, sufficient calories from wholesome foods, electrolyte balance, and moderate activity, most healthy individuals can successfully remain in long-term ketosis without complication. 

Understand that transitioning from a high-carb to keto metabolism involves a natural adaptation period before benefits are realized. 

Work with a functional medicine doctor to rule out complicating disorders, obtain baseline testing, and monitor health markers periodically. 

While not right for everyone, approached intelligently, the ketogenic diet offers transformative benefits for health, cognition, longevity and more.