If you’ve ever felt great at mile 8 and terrible at mile 18, you already get it. Endurance isn’t just fitness. It’s fuel, pacing, and a stomach that stays cooperative when you’re tired and still moving.
Ketone supplements are showing up in endurance circles because athletes want another tool when long-day energy feels uneven. Some people use exogenous ketones to help support a steadier feel when fueling gets hard to manage late in a session.
Still, ketone supplements aren’t magic. Carbs still pay the rent when intensity goes up.
This article breaks down where ketone supplements may fit before, during, and after long efforts, plus how to choose one and test it in training so race day is not an experiment.
Key Takeaways
- Who should be cautious (and common side effects)
- Ketone supplements may help support steadier energy during long efforts for some athletes, especially when paired with a smart carb plan.
- Timing depends on the product and the goal. Many athletes test ketone supplements before, during, and after training.
- Ketones aren’t a replacement for carbohydrates at higher intensities, so don’t use ketone supplements as an excuse to under-fuel.
- Start low, test in training, and track outcomes like pacing consistency, perceived effort, and gut comfort.
What Endurance Athletes Actually Need From a Fueling Plan
Long endurance days usually break down for predictable reasons. Energy intake falls behind output, hydration and sodium drift off plan, or the gut taps out and refuses more fuel. When any one of those happens, pacing gets messy and it’s hard to recover the day.
The goal of a fueling plan isn’t perfection. It’s repeatable steadiness. You want enough carbs to support output, enough fluids and electrolytes to maintain performance, and a strategy that works when you’re tired and decision-making gets sloppy.
Research and position statements in sports nutrition consistently highlight carbohydrates as the main performance fuel at moderate to high intensities. That’s why most endurance plans start with carbs, then build around them with hydration and sodium. The challenge is that real life doesn’t always match the plan, which is why athletes look for additional tools.
What Are Ketones (and What Are “Exogenous Ketones”)?
Ketones are fuel molecules your body can make, especially when carbs are lower, when you’re fasting, or when training volume is high. They’re part of how the body keeps energy available in different conditions
Exogenous ketones are ketone supplements that provide ketones from outside the body. You’ll typically see them as ketone drinks or supplements, and the goal is to raise ketone levels without needing a strict keto diet.
In plain English, ketones can be used by the brain and muscles as fuel.
That doesn’t mean ketones beat carbs in every situation. It means ketones can be one more option in your fuel mix, which can matter when you are going long.
Ketones vs Carbs for Endurance: When Each Fuel Makes Sense
Carbs are still the main player when intensity matters. If you’re trying to hold a strong pace, climb hard, or close fast, your body relies heavily on carbohydrates because they support fast energy demands
Ketone supplements may make more sense when you are doing steadier-state work, long sessions, or anything where you want another option to support a smoother feel. A common approach is “ketones plus carbs,” not “ketones instead of carbs.”
If you drop carbs too low and hope ketone supplements will carry the day, many athletes feel flat when intensity rises. If carbs stay realistic and ketones are treated as an add-on, outcomes are easier to evaluate.
Potential Benefits of Ketone Supplements for Endurance (What the Science Suggests)
Athletes explore exogenous ketones for a few simple reasons: long sessions can get messy late, carb intake can fall behind output, and the gut can start pushing back. That’s when energy can feel spiky, and decision-making gets sloppy.
Research suggests exogenous ketones can raise circulating ketone levels, giving the body and brain another usable fuel source alongside carbohydrates
Human exercise studies have explored:
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Steadier perceived energy with enhanced endurance, allowing athletes to go longer before hitting fatigue
Cox2016 . -
Another option when the gut limits carbs, on very long days, GI tolerance can cap how many carbs someone can comfortably take in
Cox2016 . -
Potential glycogen sparing in some contexts. Some studies suggest ketones may shift substrate use and reduce reliance on glycogen at a given workload. This does not guarantee faster race times, but it may matter for long-duration pacing and late-session resilience
Evans2019 . - Recovery and adaptation (still evolving). Research continues to examine ketones alongside training and recovery variables.
Overall, exogenous ketones may help support a steadier energy feel during long efforts by adding a second fuel option. Results vary by product type, dose, timing, carb strategy, and training status.
How to Use Ketone Supplements for Endurance (Before, During, After)
If you’re going to test ketone supplements, keep the experiment clean. Change one thing at a time. Keep your carb plan consistent. Track outcomes over multiple sessions.
Also, don’t introduce ketone supplements for the first time on race day. Your gut needs practice with any new routine.
Before training or racing: Many athletes test ketone supplements before long sessions to support a steadier start and a smoother feel. Start with a low dose in training and adjust only if tolerance is good.
During long efforts: Some athletes experiment with ketone supplements during very long sessions, but carbs typically stay central. If you try ketone supplements during, keep the rest of your fueling plan stable so you can tell what’s helping.
After training: Post-session, don’t skip the basics. Protein, carbs when appropriate, hydration, and sleep are still the foundation. Ketone supplements can be optional, and only worth keeping if you see a clear benefit.
A helpful self-check is to track three things: pacing consistency, perceived effort late in the session, and gut comfort. If you notice an improvement in one without hurting the others, that is a real signal.
How to Choose the Best Ketone Supplement (What to Look For)
The best ketone supplement for you is the one you can use consistently, tolerate well, and fit into your routine.
When choosing a supplement, start with logistics. A ketone shot might be easier than mixing a drink mid-session, and pre-session use is often easier than during-session use. If the format doesn’t match your training reality, you won’t use it.
Next, look at label clarity. Good ketone supplements are clear about serving size, ingredients, and how to use the product. In endurance, “mystery blends” are not helpful because you need repeatability.
If you compete, consider third-party testing standards such as NSF Certified for Sport®. For many athletes, that is a useful signal of quality and screening.
Finally, prioritize tolerance. If a product doesn’t sit well, it won’t support endurance, because stomach comfort is part of performance. Start low, test in training, and choose the option that feels stable across multiple attempts.
There are a few different types of exogenous ketone supplements to choose from:
- Ketone salts: typically BHB bound to minerals (such as sodium, potassium, magnesium, or calcium). Many are powders. They may be easier to find, but mineral load and GI tolerance can vary.
- Ketone esters: typically BHB (or AcAc precursors) bonded to another compound. They often raise ketone levels quickly, but taste and tolerability can be limiting for some people.
- Ketone diols: 1,3-butanediol (BDO), which your body can convert into beta-hydroxybutyrate (BHB).
Ketone-IQ is ketone diol based and uses R-1,3-butanediol (BDO) as its ketone source, which is why you will see ketones listed on-label as “Ketones (as R-1,3-butanediol).”
Who Should Be Cautious (and Common Side Effects)
The most common issue with ketone supplements is GI discomfort, especially when dose is high or timing is rushed. If that happens, it doesn’t necessarily mean ketone supplements won’t work for you. It often means the dose, timing, or total fueling stack needs adjustment.
A safer approach is simple. Start with a small test dose, try it on an easier training day, and avoid stacking multiple new supplements at once. If you change carbs, caffeine, hydration, and ketone supplements together, you won’t know what caused the result.
If you have a medical condition, are pregnant or nursing, or take medications, it’s smart to talk with a clinician before adding any supplement routine. General guidance from credible nutrition and supplement resources also supports paying attention to how you feel over time, not just on day one.
FAQs
Do ketone supplements help with endurance?
Ketone supplements may help support steadier energy during long endurance sessions for some people, especially when paired with consistent carbs and hydration. Because responses vary, it’s best to test exogenous ketones in training first.
Are ketones better than carbs for long-distance running?
Carbs are still essential for higher intensity running, even in long events. Ketone supplements can be a complementary tool, but they aren’t a straight replacement for carbs.
When should I take ketone supplements for a marathon or long ride?
Many athletes start by testing ketone supplements before long training sessions, since timing and dose are easier to control. If that goes well, some people experiment during very long efforts.
Can I take ketones and carbs together?
Yes. Many endurance athletes use ketone supplements alongside carbs. The key is not to under-fuel carbs when intensity is high.
What is the best ketone supplement for endurance athletes?
The best ketone supplement is the one you tolerate well, can use consistently, and can fit into your endurance routine. Prioritize label clarity, practical format, and repeatable results.
Do exogenous ketones cause stomach issues?
They can, especially at higher doses or with poor timing. Starting with a smaller dose and practicing in training can help.
Can ketone supplements help prevent bonking?
They may support steadier energy for some athletes, but they don’t replace pacing plus consistent carb intake. Those two are still the most reliable tools.
Do I need to be in ketosis for ketone supplements to work?
No. Exogenous ketones provide ketones directly, and many people use ketone supplements without being in ketosis.
Learn More
How to Run Faster: Mental and Physical Techniques
Fueling the Future: How Ketone Supplements Are Redefining Sports Nutrition
Disclaimer:
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
