How Much Water to Drink With Energy Gels (and Why Cool Races Change It)

If you take your gels with a sip or two of water, it probably worked over the summer, because hot long runs kept you drinking.

On a cool fall or winter race day, you sweat less and you feel less thirsty, so you’re tempted not to drink as much water.

But a gel is far more concentrated than anything else you swallow on a run, and without enough water it can sit in your stomach instead of fueling your legs.

So how much water do you need with each gel, and why does a cool race change the answer?

That’s what we’re going to dig into in this article, including:

• Why a gel needs water before your body can use it
• Why a cool race leaves you drinking less of it
• How much water to take with each gel, and what you gain when you get it right
• And how to practice your plan on long runs before race day.

Why Does an Energy Gel Need Water?

Your stomach won’t pass a gel on to your small intestine, where the carbohydrate is absorbed, until it has been diluted, and 3 things decide how long that takes.

1. A Gel Is Far More Concentrated Than Your Blood

Researchers measure how concentrated a gel is by its osmolality, the number of dissolved particles in each kilogram of water.

Your blood is about 290 mosmol/kg.

A 2015 survey measured the osmolality of commercial energy gels.

The average gel was about 15 times as concentrated as your blood, at 4,424 mosmol/kg.

That means most gels can’t be absorbed the way they come out of the packet, so your stomach has to dilute them with water before the gel can move on into your small intestine.

The researchers noted that this range of concentrations has obvious implications for stomach discomfort and for how much fluid runners need to drink with their gels.

2. Concentrated Carbohydrate Leaves Your Stomach Slowly

A 1995 study measured how long 20 oz (600 ml) of different glucose drinks took to leave the stomach.

A concentrated glucose drink took 130 minutes to half-empty from the stomach, against 17 minutes for a dilute 4% drink.

No one has run this test on a gel, but the average gel is more than 3 times as concentrated as the slowest drink in that study.

So the water you take with a gel is what brings it closer to the dilute drink that left the stomach in 17 minutes.

3. Running Hard Slows Your Stomach Even More

A 2015 analysis of 20 studies found that higher exercise intensity and longer exercise both slowed how fast the stomach emptied.

That means the late, hard miles of a race are when an undiluted gel sits in your stomach the longest.

Sports drinks are different, because they come already diluted.

A 1998 study found that 6% carbohydrate drinks were absorbed as well as plain water.

That means you don’t need extra water with a 6% sports drink, only with your gels.

Why Does a Cool Race Change How Much Water You Drink?

In cooler weather you sweat less, so you feel thirsty later.

If you drink when you’re thirsty, that means less water at every aid station, and each gel goes into a stomach with less water to dilute it.

A fueling plan that worked through a hot summer can leave gels sitting in your stomach on a cool race morning.

That’s why the water you take with each gel needs a plan of its own on a cool day, instead of following your thirst.

How Much Water Should You Drink With Each Gel?

Drink at least 8 oz (250 ml) of water with every gel that has 25 g of carbohydrate, and work toward 16 oz (500 ml) when you can.

That range comes from 2 carbohydrate concentrations used in sports nutrition research.

A 2025 study on gut tolerance had runners take their gels at a 10% carbohydrate concentration, which is what a 25 g gel works out to in 8 oz (250 ml) of water.

A 2001 review recommended 3% to 5% carbohydrate to help you absorb water during long events, which is what a 25 g gel works out to in 16 oz (500 ml).

Here is how the concentration changes with the water you take with one gel that has 25 g of carbohydrate.

Water with a 25 g carbohydrate gel	Carbohydrate concentration	What it means
A sip, about 2 oz (60 ml)	About 42%	Far stronger than any drink tested for stomach emptying.
4 oz (125 ml)	20%	Twice the strength used in gut-tolerance research.
8 oz (250 ml)	10%	The concentration used in a 2025 gut-tolerance study of runners.
16 oz (500 ml)	5%	The top of the range recommended for absorbing water.

Gels with more carbohydrate need more water. A gel with 40 g of carbohydrate needs about 13 oz (400 ml) to reach the same 10%.

What Do You Gain From Drinking Enough Water With Your Gels?

Getting the water right does more than keep a gel from sitting heavy.

More of Each Gel Becomes Fuel

Your muscles can only use the carbohydrate in a gel once it leaves your stomach and is absorbed in your small intestine.

Taking a gel with 8 to 16 oz (250 to 500 ml) of water brings it down to 5% to 10% carbohydrate, much closer to the dilute drink that half-emptied in 17 minutes, so the carbohydrate reaches your muscles while you still need it.

Your Gut Lining Stays Protected

The water you drink with your gels also keeps you from running dry.

A 2008 study had runners do the same 60-minute treadmill run with no fluid, with water, and with a 4% glucose drink.

When they ran without fluid, their stomach and small intestine became leakier than at rest. Drinking water or the glucose drink kept their gut at its resting level.

That means the water you drink during a race also protects your gut lining, on top of diluting your gels.

Fewer Stomach Problems on the Run

A 2025 position statement from sports dietitians and ultra-endurance researchers reviewed what works for exercise-related stomach problems.

Staying hydrated before and during exercise was one of the few strategies with mostly consistent benefits.

That means drinking enough water with your gels is one of the gut fixes the research backs most reliably.

How to Practice Your Gel and Water Plan Before Race Day

Use your last 2 long runs before the taper as the rehearsal, at a pace and temperature as close to race day as you can get.

Carry a bottle with the volume marked, take each gel with the 8 to 16 oz (250 to 500 ml) you plan to drink on race day, and note any run where a gel sits heavy.

If 16 oz (500 ml) per gel feels like more than your stomach can hold on the run, that’s a sign to train your stomach to handle more fuel and fluid over the next few long runs.

Water dilutes the gel, but your gut still has to digest what’s in it.

A 2012 review found that blood flow to your gut can drop by 80% or more during long or hard exercise, so your gut has less blood to digest with while you run.

That’s why we formulated MAS Flush with 4 digestive enzymes, including amylase, which breaks down the starches and carbohydrates you eat.

We added cellulase, protease and lipase for the fiber, protein and fat in your meals, and 1,500 mg of psyllium husk to firm up loose stools before you run.

You take 4 capsules every evening. It works through daily use, so start it well before race day.

Your Gel and Water Plan for a Cool Race

When the weather cools, plan the water you take with each gel the same way you plan the gels.

Situation	What happens	What to do
Taking a gel with a sip of water	The gel stays at about 42% carbohydrate, far stronger than any drink tested for stomach emptying.	Drink at least 8 oz (250 ml) with every gel that has 25 g of carbohydrate.
Racing on a cool day	You sweat less, feel thirsty later and drink less with each gel.	Drink a set 8 oz (250 ml) with every gel.
Using a gel with 40 g or more of carbohydrate	It needs more water to reach the same strength.	Drink about 13 oz (400 ml) with a gel that has 40 g of carbohydrate.
Rehearsing before the taper	Your last 2 long runs are the time to test the plan.	Carry a marked bottle and drink the planned volume with each gel.