If you’ve ever started the ketogenic (keto) diet—or know someone who has—you may have heard about the dreaded “keto flu.” Don’t worry, it’s not an actual virus. The term simply describes temporary side effects that some people experience in the first week or so of starting keto.

Why does it happen?

When you reduce carbs dramatically, your body has to shift from using glucose (sugar) as its main source of energy to using fat and ketones. That transition is called nutritional ketosis, and it can feel a little bumpy at first.

Here’s why:

Adaptation stress: The sudden shift in fuel source can leave you feeling sluggish until your cells adjust.

Carb withdrawal: Your body is used to quick energy from carbs, and it takes a few days to learn how to run on fat instead.

Water and electrolyte loss: Carbohydrates hold onto water and electrolytes (like sodium, potassium, and magnesium). When carbs are cut, the body flushes out extra fluid, leading to dehydration and mineral loss.

Adaptation stress: The sudden shift in fuel source can leave you feeling sluggish until your cells adjust.

Common symptoms of the keto flu

Everyone is different, but the most common complaints include:

• Fatigue or low energy
• Headaches
• Irritability or “brain fog”
• Nausea
• Muscle cramps
• Trouble sleeping

The good news? These symptoms are temporary. Most people notice improvement within 3–7 days as their bodies adjust to ketosis.ate if you’re sensitive—they can be high in histamine or trigger release.

How to beat the keto flu

You don’t have to suffer through it! Here are some practical ways to ease the transition:

1. Stay hydrated 💧Aim for at least 8–10 cups of water per day. Remember, you’re losing extra fluid at the beginning, so replenishing is key.
2. Boost electrolytes ⚡Salt your food a little more than usual, sip on broth, and include potassium- and magnesium-rich foods like leafy greens, avocado, and nuts. Some patients also benefit from an electrolyte supplement such as ElectroPure Hydration by Designs for Health.
3. Ease into keto gradually 🍳Instead of slashing carbs overnight, try lowering them step by step over a week or two. This gives your metabolism more time to adjust.
4. Eat enough fat and protein 🥑Don’t skimp on calories. Healthy fats (avocado, olive oil, salmon, nuts) and adequate protein help stabilize energy and keep you full.
5. Prioritize sleep and rest 😴Fatigue can worsen symptoms. Try to get 7–9 hours of quality sleep and listen to your body during the transition.