Lightheadedness on Keto and Intermittent Fasting: Causes and Fixes
Summary
Feeling lightheaded when starting a ketogenic diet and intermittent fasting is a common experience typically caused by a drop in blood volume and pressure. This happens because cutting carbohydrates causes the body to release stored fluid along with electrolytes. The fix is straightforward: replenish fluids and electrolytes, particularly sodium and potassium.
Key Takeaways
- Lightheadedness on keto is primarily a fluid and electrolyte issue, not a sign of something dangerous
- When you eliminate carbohydrates, your body stops retaining fluid, leading to reduced blood volume and lower blood pressure
- Drinking plain water alone can make symptoms worse by further diluting your remaining electrolytes
- Sea salt added to water is a quick and effective way to restore blood volume
- Potassium should also be included alongside sodium for proper electrolyte balance
- Lightheadedness that existed before starting keto may point to separate issues such as weak adrenals, anemia, or low blood sugar
Details
Why Lightheadedness Happens
When you eat a high-carbohydrate diet, your body retains water. Transitioning to keto causes a rapid release of this stored fluid. Along with the fluid, key electrolytes — particularly sodium and potassium — are flushed out. The resulting drop in blood volume leads to reduced blood pressure, which the brain experiences as lightheadedness or dizziness.
The Wrong Fix: Plain Water
Many people instinctively drink more water when they feel dizzy, but doing so without electrolytes worsens the problem. Drinking plain water dilutes the already-low concentration of electrolytes remaining in the body, amplifying symptoms rather than relieving them.
The Right Fix: Salt + Water + Electrolytes
Dr. Berg recommends the following approach:
- Add approximately ⅛ teaspoon of sea salt to a glass of water
- Dissolve it fully and drink it down
- Include potassium and other electrolytes alongside the sodium
- This combination rapidly restores blood volume and should relieve lightheadedness relatively quickly
When Lightheadedness Has a Different Cause
If lightheadedness was present before beginning keto or intermittent fasting, the root cause is likely unrelated to fluid loss. Potential alternative causes mentioned include:
- Weak or fatigued adrenal glands — adrenal fatigue
- Anemia — insufficient red blood cells or iron
- Low blood sugar — hypoglycemia
These cases require a different approach and should be investigated separately.