Can You Take Pre-Workout On An Empty Stomach?

Updated on  February 26, 2023
William Toro

Published By:  William Toro

Fact Checked by: Bridget MacDonald, RDN

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The secret behind those six-pac abs, lean body composition, and staying motivated to keep exercising is none other than an effective pre-workout. Intermittent fasting and zero food caloric energy keep you going, but there is more to fitness. No matter what the heart-throb celebrities claim regarding muscle gain and weight loss, pre-workouts always step up their fitness game.

You might be wondering about the prerequisites of pre-workouts. The first thing that comes to mind about consuming supplements is whether you can take them on an empty stomach or not?

The benefit of taking a pre-workout before a meal is that its absorption from the stomach lining is more effective. However, according to research, taking a pre-workout on an empty can result in side effects for some people [1]. Consuming pre-workout on a full stomach does not reduce its effect and decreases any gastric irritation, but it would take more time to absorb into the gut.

Based on scientific research, we have laid out some facts regarding pre-workouts, workout, and their effects on the human body on an empty stomach. It will help fitness enthusiasts understand the absorption and function of pre-workouts better.

What Are The Constituents Of An Ideal Pre-Workout?

Before we conclude whether a pre-workout should be taken before meals, let's dive into the pre-workout ingredients closely.

Do you know? When you gulp down your pre-workout, the following nutrients are absorbed into your bloodstream to deliver excellent physical performance and fasted training. Here are the constituents of a good pre-workout drink.



Your pancreas, liver, and kidneys work in coordination to elevate your stamina during workouts by producing the organic compound phosphocreatine. This power booster naturally produced by the human body is stored as creatine in the muscle tissue.

Creatine consumption multiplies the natural reservoirs of phosphocreatine. Phosphocreatine isn't some kind of lightning bolt that charges you instantly, like in fiction movies. Instead, it is used by the human body for ATP energy production [2].

ATP is the body's energy currency that produces the energy required during a workout for enhanced exercise performance. Consuming creatine before workouts can provide ample energy and workout strength, build muscle and endurance, and prevent muscle exertion [3].



Caffeine occupies the receptors of neurotransmitter adenosine [5] which makes you sleepy. Adenosine is responsible for the human body's sleep-wake cycle. Once caffeine attaches to most of its receptors, one feels awake and energized. Moreover, it increases alertness throughout your workout session and promotes the catabolism of stored fat [4].



The amino acid beta-alanine is formed in the liver and is responsible for producing that tingling feeling during a workout. It functions along with caffeine to increase exercise endurance and prevents fatigue due to heavy workout training [6].



Nitrosigine assists the shift of blood circulation towards the muscle tissue. It relaxes blood vessels and causes vasodilation to increase muscle pump and cardiac health while boosting exercise performance [7]. It also improves workout energy for fasted training, allowing you to achieve more reps.



L-theanine is an amino acid normally found in tea leaves. When consumed in combination with caffeine to workout on an empty stomach, it reduces gastric distress and other side effects caused by caffeine [8]. This amino acid can provide more energy without overstimulation when added to a sports supplement. 



The amino acid l-citrulline causes the formation of Nitric Oxide in the human body. Nitric oxide causes vasodilation. In other words, it relaxes blood vessels, facilitating the blood flow towards the muscles [9]. Thus, it works in delivering oxygen and nutrients to the working muscles for enhanced exercise performance. It also reduces muscle fatigue by lowering lactic acid build-up in muscle tissues, helping fitness enthusiasts to workout longer [10].

Are Pre-Workout Supplements And Branched-Chain Amino Acids Any Different?

Many fitness enthusiasts are doubtful about the differences between branched-chain amino acids abbreviated as BCAAs and a pre-workout supplement. Valine, Leucine, and Isoleucine constitute BCAAs, and a pre-workout has different compositions, as already mentioned in the ingredients of pre-workouts above.

A pre-workout is beneficial for various functions like boosting energy, elevating mood, and increasing focus and endurance for effective workouts. On the other hand, BCAAs have added benefits like their role in the recovery of sore muscles after a workout and stimulation of muscular growth [11].

If we see the ingredients individually, the BCAA leucine synthesizes muscle tissues and promotes muscle building [12]. Isoleucine supplies the raw materials for energy production by breaking them into more minor compounds [13].On the other hand, Valine prevents the transport of tryptophan [14] to the brain, reducing the post-workout feeling of fatigue.

Thanks to all of these benefits, the BCAAs are also taken along with pre-workouts as the best pre-workout supplements for muscle growth, exercise endurance, reduction of fatigue, and performance-enhancing benefits.

What Are The Effects Of Resistance Exercises On Muscles, And What Is The Role Of Pre-Workout Supplementation In High-Intensity Exercises?

High-intensity exercise like weight lifting significantly affects lean muscle mass growth [15]. It also promotes healthy circulation of blood inside the body, especially to the muscle tissue of the limbs. The lean muscle mass growth occurs only when the protein synthesis in the muscles is greater than the protein breakdown. This growth can be made possible if one has enough stores of proteins before a workout.

Protein stores can be achieved by an excellent pre-workout supplementation and a proteinaceous diet that increases nutrient intake to maintain good body composition. If protein is absent from an external source such as diet and supplements, the protein balance is negative, and lean muscle growth does not occur even after strenuous exercises. It would rather have a damaging effect on muscles as there will be heightened muscle catabolism.

Effect Of Workout On An Empty Stomach On Hormones

A workout on an empty stomach leads to maintained sugar levels, preventing spikes or low blood sugar. Thus, it improves insulin sensitivity and aids in mechanisms that build muscle. The utilization of fat stores by doing a workout on an empty stomach leads to weight loss and an increase in lean mass. Moreover, According to clinical trials, workout on an empty stomach also affects growth hormones, Insulin, and Insulin-like growth factors.

Growth Hormone

Workout on an empty stomach causes the release of growth hormone in significant amounts, which causes fat burning by breaking down lipids and conserving proteins [16]. This hormone helps promote lean muscle mass growth, giving you those gains you dream of.

Insulin-Like Growth Factor

The insulin-like growth factor is found circulating in more significant amounts in the blood of those who workout on an empty stomach. Exercise influences the production of IGF as the release of growth hormone is also increased. It maintains blood glucose levels and stimulates muscle building. Moreover, Insulin-like growth factors are known through research to provide fuel for the anabolic phase of exercise. [17]


During a workout on an empty stomach, there is fifty times more uptake of glucose into muscles through a muscle pump of glucose called GLUT-4. It causes low blood sugar. This transport of glucose into the muscles is independent of Insulin.

However, these bouts of workout can increase insulin sensitivity, lasting up to 16 hours after the workout. Insulin is involved in the anabolism of muscles [18], and the increase in its sensitivity after a workout is beneficial for muscle growth.

A workout on an empty stomach can thus be of great benefit for the human body for muscle building, fat burning, and losing weight.

What Are The Possible Side Effects Of Taking Pre-Workout On An Empty Stomach?

A pre-workout can readily absorb into the bloodstream and provide instant results on an empty stomach. However, taking one on an empty stomach might have some side effects such as:

Jitteriness And Palpitations

Most pre-workout supplements include caffeine as the stimulant ingredient. Taking a pre-workout on an empty stomach can cause increased heart rate leading to palpitations. It also causes tremors [19]. These side effects can be avoided by taking small amounts of pre-workout supplements as a test dose in the beginning and checking for their effects on your body.

Furthermore, a pre-workout supplement should not be taken before sleeping at night as it causes restlessness and sleeplessness.

Retention Of Water

Creatine present in most pre-workout supplements increases lean muscle mass and capacity and endurance of exercise. However, it can cause bloating, retention of water, weight gain, gastric irritation, and stomach burns when taken on an empty stomach [20]. Creatine should also not be consumed in excess, whether taken individually or as a part of a pre-workout.

Reaction To Pre-Workout Ingredients

Some ingredients in pre-workouts like beta-alanine cause reactions like tingling when consumed. Beta-alanine is known for increasing exercise endurance and reducing post-workout fatigue. However, it might cause mild reactions when taken through pre-workout on empty stomach.

The reactions include numbness and needles-like sensations in your hands and feet [21]. It is not severely detrimental to the nervous system and goes away on its own. B-alanine should thus be taken in divided doses and on a full stomach.

Gastrointestinal Irritation

Caffeine, sodium bicarbonate, creatine, and magnesium are a few of the ingredients in a pre-workout that can irritate the digestive system when consumed on an empty stomach.

These effects can be avoided if the pre-workout formula is adequately diluted. A less dilute pre-workout formula on an empty stomach can lead to loose stools and digestive system irritation.

Migraine Trigger

The amino acid citrulline is a part of most pre-workout supplements and functions by increasing nitrous oxide that relaxes blood vessels in muscles and the brain. It allows more blood to flow to these parts of the body and provides it with the strength for a workout.

However, on an empty stomach, it contributes to migraines in some people through increased blood vessel diameter pressing on surrounding nerves and fluctuating blood flow to the brain [22]. This adverse effect can be avoided by taking a pre-workout supplement on a full stomach rather than an empty stomach, as in intermittent fasting.

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Bottom Line

Taking pre-workout supplements on an empty stomach makes them absorb well through the digestive system into the bloodstream. However, the benefits of consuming a pre-workout on an empty stomach are outweighed by its side effects. It can affect the gastrointestinal system and nervous system leading to digestive system irritation, tremors, palpitations, retention of water and migraines, etc. Therefore it is better to take pre-workout supplements on a full stomach to avoid adverse effects while ensuring an effective workout session.

William Toro

William Toro ‧ CPT & Nutritionist

William is a certified personal trainer from NASM, he has also been a rehab physiologist for sports persons. He has more than 15 years of experience training people. And has featured in multiple publications like FoxNews, CNBC, Bustle, and other. 

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