If you just started following a ketogenic you might experience a flu like symptoms. Ketogenic diet as you know is very low in carbohydrates, high in fat and moderate in protein. For someone new, this drastic change in their diet can lead to a flu like symptom which is caused by the body adapting to a new diet.

When you cut out carbs completely, your body starts breaking down fat for energy. This huge metabolic shift and can come as a shock to the body and may cause withdrawal-like symptoms, similar to those experienced when you stop taking an addictive substance like caffeine.

It’s not really a flu, and it’s not contagious or dangerous, but it can definitely be very unpleasant.

Symptoms includes

  • Feeling tired
  • Headache
  • Easily annoyed and feeling Irritated
  • Fatigue
  • Difficulty focusing (“brain fog”)
  • Lack of motivation
  • Dizziness
  • Sugar cravings
  • Nausea
  • Muscle cramps

Most people feel one or more of these symptoms during the first week of a keto diet, especially days 3-5.


  • Diuretic effect

You must have notice that you pee more after you started following ketogenic diet. This is because as your body adapts to using fat as fuel, there is a drop in insulin that causes your kidneys to work overtime. It basically means your body produce more urine and this diuretic effect can cause dehydration and an electrolyte imbalance.

  • Carbs Withdrawal symptom:

Like any addiction; when you’ve been eating carbs for a long time, you’re kind of addicted to it and sudden removal of carbs from your diet can make you feel different and show symptoms of flu. It does have a strong psychological component.

  • Increase in cortisol level:

When you start a ketogenic diet, the drastic change of diet and the complete removal of carbs tells your body that you’re in starvation mode.  And this can triggers the release of stress hormones, i.e. cortisol. Leading to feeling irritated and insomnia.

  • T3 thyroid hormone levels may decrease:

Low-carb diets induces a starvation like situation in your body which can lead to decrease in T3 Thyroid hormone.           

And this lower hormone levels may leave you with brain fog and fatigue.


  • Increase your salt and water intake

Stay hydrated by drinking a minimum of 3 litres of fluid every day (that could be water, coffee, green tea or any fluid), also ensure adequate electrolyte in your diet; like magnesium, potassium and sodium. This will keep your body fluid electrolyte balance healthy. And would also compensate for the excessive urinating.

  • Go slow

Reduce your carb intake to about 50 gram on the first few days and gradually reduce to about 20 grams and below.

  • Eat more fat

Make sure to eat enough fat. This can speed up adaptation phase, you’ll start to burn fat instead of glucose more quickly.  

Eat more good fat like MCTs or add butter to whatever you’re eating.

  • Do some light exercise

If you feel like you can do it, you might try some light exercise. Exercise helps your body become more metabolically flexible, it will also help relieve stress and reduce cortisol level and hence eases the symptoms.

  • Get good rest

A good night’s sleep will keep your cortisol levels in check, which will likely lessen your flu symptoms. Sleep for about 7- 8 hours.

Be patient, its body’s natural response to carbohydrate restriction. Like I’ve said before it’s not really a flu, and it’s not contagious or dangerous. Fortunately, it’s temporary, and you’ll soon feel fine again.