How Much Water Should I Drink On Keto? (From Nutritionist)

The short answer is that you’ll need to drink more water than usual while on a keto diet. But you may be wondering what that means in practice.

One expert shares a general rule of thumb that you can follow [1]:

“[At the beginning of your keto diet], you should drink at least 2.5 liters of water or fluid per day to replace the amount lost in urine. Once you become keto-adapted, you should still consume a minimum of two liters of water daily in order to prevent dehydration and promote optimal metabolic health.”

- Franziska Spritzler, RD, Certified Diabetes Educator 

So, you could try to drink 2.5 liters (~85 ounces) of water per day.

But you could also establish your individual hydration needs on a ketogenic diet based on your body weight.

That could be a better option than following a hard and fast rule that might be too general.

Use the following formula to calculate your ideal intake of water:

Your bodyweight x 75% = Ounces of water per day

Here are a couple of examples to illustrate how to use this formula to calculate your hydration needs:

• If you weigh 120 pounds, you’ll need 90 ounces of water per day (120 x 0.75 = 90)
• If you weigh 180 pounds, you’ll need 135 ounces of water per day (180 x 0.75 = 135)

As you can see, a 180-pound person needs significantly more water on keto than what the rule above suggested. That’s why I prefer following the formula over the general rule.

Once you’ve calculated your ideal fluid intake, all that’s left to do is stick to it.

But you might discover that that’s more difficult than it sounds. That’s why I’ll give you a few tips on how to stay hydrated below.

For now, let’s see why a keto diet increases your hydration needs in the first place.

The first step in preventing dehydration is knowing how to recognize it.

Symptoms of mild dehydration include [7]:

Our main concern with low-carb diets is dehydration. However, you can still overhydrate even if you’re on a ketogenic diet.

Overhydration isn’t good either. Drinking too much water can lead to a state called hyponatremia, which occurs when your blood sodium levels are too low [11].

Low sodium levels are common with folks on a keto diet for two reasons: 

• A ketogenic diet implies that we’re cutting out processed foods and salty carbs (i.e., consuming less sodium than usual).
• We lose more sodium through urine in ketosis [12].

So, the problem is that you already don’t have enough sodium while on keto.

Drinking only sodium-free water or simply too much water will further dilute your sodium levels and cause symptoms of hyponatremia, such as [13]: 

• Muscle weakness, spasms, and cramps
• Fatigue
• Nausea
• Irritability
• Headaches
• Seizures
• Coma

Luckily, there are things you can do to prevent hyponatremia even while on a low-carb diet.

For one, you can watch your sodium consumption. Try eating more healthy sodium-rich foods, such as buttermilk, cottage cheese, or canned vegetables [14].

Of course, you don’t want to overdo it with sodium-rich foods since you’re still trying to lose weight. And too much sodium may prevent weight loss and beat the purpose of a keto diet [15].

Staying hydrated doesn’t only depend on your water intake. There are other things you can and should do. We’ll go through the three most important ones below.

1. Eat Water-Rich Foods

The problem with a keto diet is that it limits our consumption of various fruits and vegetables.

The lack of fruits and vegetables may decrease your fiber intake and lead to dehydration   [16],[17].

For example, most keto diets don’t allow you to consume bananas and peas. And both contain a lot of water.

So, not consuming them increases the risk of dehydration.

To prevent it, try replacing “forbidden” water-rich foods with those you can consume.

For example, you could eat broccoli instead of peas and berries instead of bananas [18].