Pre-Workout Ingredient Glossary: An A–Z Guide to Ingredients and Label Terms

By Connor Southworth
Last reviewed: October 2, 2026

Disclosure: Connor Southworth owns 4 Gauge, which sells pre-workout and other sports supplements. This glossary covers ingredients both used and not used in 4 Gauge.

Pre-workout ingredients serve different purposes: some increase alertness, some support repeated high-intensity exercise, and others contribute to hydration, flavor, or normal nutrient function. Their usefulness depends on the ingredient's form, amount, how consistently it is taken, and the outcome being measured.

This glossary explains 30 common ingredients and label terms, including caffeine, citrulline, creatine, beta-alanine, L-theanine, nitrates, electrolytes, and proprietary blends. It covers ingredients found in 4 Gauge and ingredients used in other formulas.

Use it to understand a label, compare products, and recognize the difference between a plausible mechanism and a demonstrated benefit.

What to know before comparing ingredients

• An ingredient's presence does not establish an effective dose. Look for the amount per full serving.
• The form matters. Citrulline malate is different from pure L-citrulline, and beetroot powder weight does not tell you its nitrate content.
• Some ingredients depend on consistent use. Creatine and beta-alanine work through changes that develop with supplementation, rather than a brief stimulant sensation.
• A noticeable feeling is not a performance test. Tingling, flushing, or a strong caffeine buzz does not establish that a formula improves training.
• Research on individual ingredients does not prove the complete formula works the same way. A finished product needs its own research to establish product-specific effects. [1, 5, 9, 10]

For studied amounts and regimens, see our pre-workout ingredient dosage guide.

How to read the evidence notes: Each note describes the limits of the evidence for that particular purpose. An ingredient can be essential for normal health without providing an additional performance benefit when taken as a supplement.

A–Z ingredient and label glossary

Acetyl-L-carnitine (ALCAR)

Definition: An acetylated form of carnitine, a compound involved in transporting fatty acids into mitochondria, where they can be used to produce energy.

Purpose: Included in some formulas for energy metabolism and proposed cognitive benefits.

Evidence caveat: Carnitine studies use different forms, populations, and supplementation schedules. Findings involving L-carnitine or L-carnitine L-tartrate cannot automatically be applied to acetyl-L-carnitine. Its biological role does not establish that a pre-workout serving improves focus, exercise performance, or fat loss in healthy adults.

Learn more: NIH: Carnitine—forms, research, and safety. [2]

Arginine (L-arginine; AAKG)

Definition: An amino acid the body uses to make proteins and nitric oxide. AAKG stands for arginine alpha-ketoglutarate, a supplemental form.

Purpose: Commonly marketed for blood flow and muscle “pump.”

Evidence caveat: Exercise findings are mixed, and results depend on the form, dose, and protocol. A role in nitric oxide production does not guarantee better lifting performance. Evidence about L-arginine should not be treated as proof that every AAKG formula has the same effects.

Learn more: Systematic review and meta-analysis of arginine and athletic performance. [3, 4]

BCAAs: Branched-chain amino acids

Definition: Leucine, isoleucine, and valine—three of the nine essential amino acids.

Purpose: Marketed for muscle recovery and muscle protein synthesis.

Evidence caveat: BCAAs alone do not supply all the essential amino acids needed to build new muscle protein. Evidence for additional benefits is limited when the diet already provides sufficient high-quality protein. A BCAA blend is not equivalent to a complete protein source.

Learn more: NIH: Exercise supplements, including BCAAs and protein. [1]

Beta-alanine

Definition: An amino acid used to make carnosine, which helps buffer acidity inside working muscles.

Purpose: May support performance during certain sustained or repeated high-intensity efforts.

Evidence caveat: Benefits depend on regular supplementation that raises muscle carnosine over time. Evidence is most relevant to particular exercise tasks, including intense efforts lasting approximately one to four minutes; it does not establish a universal strength or endurance benefit. The temporary tingling beta-alanine can cause is separate from its performance mechanism.

Learn more: Why does pre-workout make you tingle? and the ISSN beta-alanine position stand. [5]

Betaine (trimethylglycine; TMG)

Definition: A compound involved in methyl-group transfer and regulation of cellular water balance. Betaine anhydrous is the form commonly studied for exercise.

Purpose: Investigated for strength, power, and training adaptations.

Evidence caveat: A 2024 meta-analysis found a benefit for maximal strength, particularly lower-body strength, with repeated supplementation. It did not find significant benefits across every performance measure. Betaine hydrochloride, used in some digestive products, should not be assumed to provide the same exercise effects.

Learn more: Systematic review and meta-analysis of chronic betaine supplementation. [6, 1]

Caffeine and caffeine anhydrous

Definition: Caffeine is a stimulant that blocks adenosine receptors, helping reduce sleepiness and perceived fatigue. “Anhydrous” means the ingredient is supplied without water.

Purpose: Used for alertness and potential exercise-performance benefits.

Evidence caveat: Caffeine has substantial supporting exercise research, but response varies. More does not reliably mean better. It can cause anxiety, palpitations, stomach discomfort, or sleep disruption. Caffeine from coffee, tea, energy drinks, medications, and supplements contributes to the same daily total.

Learn more: How much caffeine should be in pre-workout? and the ISSN caffeine position stand. [7, 8]

Citrulline: L-citrulline and citrulline malate

Definition: L-citrulline is an amino acid the body can convert into arginine, supporting nitric oxide production. Citrulline malate combines citrulline with malate.

Purpose: Used in formulas targeting blood flow, muscle pump, and exercise performance.

Evidence caveat: Performance findings vary by exercise test, formulation, and study design. A gram of citrulline malate is not a gram of pure L-citrulline. For a product specified as 2:1 by weight, two-thirds of the combined weight is nominally citrulline; that calculation does not independently verify ingredient purity or composition.

Learn more: 4 Gauge's citrulline research guide and a critical review of citrulline malate and exercise performance. [9]

Coconut water powder

Definition: A dried coconut-water ingredient that may contribute minerals and carbohydrates, depending on its composition.

Purpose: Included for hydration positioning and electrolyte contribution.

Evidence caveat: Research on drinking coconut water cannot establish that a small amount of coconut water powder provides equivalent hydration benefits. Evaluate the finished formula's disclosed sodium, potassium, carbohydrate, and fluid intake. The ingredient name alone does not establish meaningful electrolyte replacement.

Learn more: Human trial comparing coconut water, a sports drink, and water. [11]

Creatine monohydrate

Definition: A supplemental form of creatine that increases muscle creatine stores, supporting the rapid regeneration of ATP—the immediate energy source used by cells.

Purpose: Supports repeated high-intensity exercise and can improve strength and lean-mass gains alongside training.

Evidence caveat: Creatine monohydrate has extensive supporting evidence. Benefits depend on increasing muscle stores through consistent intake. Its presence in a pre-workout does not mean the serving supplies the entire daily amount used in common research protocols. Creatine is not a stimulant.

Learn more: 4 Gauge's creatine research guide and the ISSN creatine position stand. [10]

EAAs: Essential amino acids

Definition: The nine amino acids the body cannot make in sufficient amounts and must obtain from food.

Purpose: Supply the building blocks required for muscle protein synthesis.

Evidence caveat: EAA supplementation can stimulate muscle protein synthesis, but that finding is different from proving an immediate workout-performance benefit. Its practical value depends on overall protein intake, meal timing, energy intake, and the person's circumstances. Complete dietary proteins also supply EAAs.

Learn more: ISSN position stand on essential amino acid supplementation. [12]

Electrolytes

Definition: Minerals that carry an electrical charge in body fluids, including sodium, potassium, magnesium, and chloride.

Purpose: Support fluid balance, nerve signaling, and muscle function. Sodium is particularly relevant to replacing sweat losses.

Evidence caveat: Requirements vary with sweat rate, exercise duration, weather, diet, and individual sweat composition. A formula containing electrolytes is not automatically a complete hydration strategy. Look at the disclosed quantities and the amount of water consumed, rather than relying on an “electrolyte blend” claim.

Learn more: ACSM position stand on exercise and fluid replacement. [13]

Fully disclosed formula

Definition: A formula that identifies the amount of each dietary ingredient per serving, rather than hiding individual amounts within a proprietary blend.

Purpose: Makes it easier to compare ingredients, evaluate stimulant exposure, and assess whether quantities resemble those studied.

Evidence caveat: Transparency helps evaluation; it does not establish effectiveness, purity, or accurate manufacturing. Those questions require appropriate evidence and quality controls.

Learn more: Proprietary blends vs. fully disclosed formulas. [14, 15]

Glycerol

Definition: A compound that can increase fluid retention when consumed with sufficient water.

Purpose: Studied for pre-exercise hyperhydration, particularly in endurance and heat-related settings.

Evidence caveat: Research involves specific glycerol-and-fluid protocols. It does not establish that any small glycerol serving produces a better muscle pump or workout. Performance findings are variable, and gastrointestinal symptoms can occur. For glycerol powders, the powder's weight and its actual glycerol content may differ.

Learn more: Systematic review of pre-exercise hyperhydration. [16]

L-theanine

Definition: An amino acid naturally present in tea.

Purpose: Often paired with caffeine in products targeting attention and a more comfortable subjective experience.

Evidence caveat: Human research supports possible benefits for some attention tasks, including with caffeine, but results differ across outcomes. Attention-test findings do not establish improved lifting performance. L-theanine does not remove caffeine from the body or guarantee protection against jitters, anxiety, or sleep disruption.

Learn more: 4 Gauge's caffeine and L-theanine guide and a 2025 systematic review and meta-analysis. [17]

Loading phase

Definition: An initial supplementation period intended to raise an ingredient's tissue stores more quickly. The term is commonly used with creatine.

Purpose: Can shorten the time needed to increase muscle creatine stores.

Evidence caveat: Creatine loading is optional; consistent lower daily intake can also increase stores over time. A loading protocol should not be interpreted as permission to take extra servings of a multi-ingredient pre-workout, because that also increases caffeine and every other ingredient.

Learn more: ISSN guidance on creatine supplementation. [10]

Magnesium

Definition: An essential mineral involved in energy metabolism, muscle function, and nerve signaling.

Purpose: Included in some sports supplements for nutrient adequacy and normal physiological function.

Evidence caveat: Being necessary for muscle function does not mean extra magnesium reliably improves performance in someone with adequate status. Benefits depend on the population and baseline intake. Supplemental magnesium can cause diarrhea, with tolerance affected by the form and amount.

Learn more: NIH: Magnesium and a systematic review of magnesium supplementation and muscle fitness. [18, 19]

Niacin: Vitamin B3

Definition: A vitamin used to make coenzymes involved in cellular energy metabolism. Common supplemental forms include nicotinic acid and nicotinamide.

Purpose: Included for normal nutrient function and often promoted through “energy” language.

Evidence caveat: Nicotinic acid can cause warmth, redness, and flushing. Nicotinamide generally does not produce the same flush. Flushing is not evidence of better muscle blood flow, fat loss, or workout performance.

Learn more: NIH: Niacin—forms and adverse effects. [20]

Nitrates and beetroot

Definition: Dietary inorganic nitrate is found in foods such as beetroot and leafy greens. The body can convert nitrate to nitrite and then nitric oxide.

Purpose: Studied for exercise efficiency and performance, particularly in endurance settings.

Evidence caveat: Benefits vary with training status, exercise demands, and supplementation protocol. Beetroot powder weight is not nitrate content. Without a disclosed or measured nitrate amount, you cannot reliably compare a beetroot ingredient with nitrate-standardized products used in research.

Learn more: Systematic review of factors affecting nitrate's exercise benefits. [21, 1]

Nitric oxide (NO)

Definition: A signaling molecule produced in the body that helps regulate blood-vessel dilation and other physiological processes.

Purpose: The target of many ingredients marketed for circulation and muscle pump.

Evidence caveat: “Nitric oxide booster” usually describes a product intended to support nitric oxide pathways; it does not necessarily mean the powder contains nitric oxide. Changes in a biological marker or blood flow do not automatically establish improved strength, endurance, or muscle growth.

Learn more: Citrulline, nitric oxide, and the limits of performance claims. [9]

Other ingredients

Definition: The label section identifying ingredients outside the Supplement Facts listing, often including flavors, sweeteners, acids, and processing aids.

Purpose: Helps explain taste, texture, mixing, stability, and other formulation characteristics.

Evidence caveat: An ingredient appearing here is not automatically harmful or unnecessary. Evaluate its identity, purpose, and relevance to your needs. This section also matters when checking sweeteners and ingredients you wish to avoid.

Learn more: FDA: Questions and answers on dietary supplement labels. [14]

Paresthesia

Definition: A tingling, prickling, or pins-and-needles sensation. Beta-alanine is a common cause in pre-workout formulas.

Purpose: This is a sensation, rather than a desired performance function.

Evidence caveat: Typical beta-alanine tingling does not demonstrate improved performance. Do not assume every unusual sensation is beta-alanine-related, especially when symptoms are severe, persistent, or accompanied by other concerning signs.

Learn more: Why pre-workout can cause tingling and the broader pre-workout side-effects guide. [5]

Proprietary blend

Definition: A labeled group of dietary ingredients that discloses the blend's total weight without listing every ingredient's individual amount.

Purpose: Allows a manufacturer to present ingredients together under a blend name while withholding individual quantities.

Evidence caveat: U.S. labeling rules permit qualifying proprietary blends. Their ingredients must be listed in descending order by weight, but that order does not reveal exact doses. A blend is not automatically ineffective; it makes ingredient-by-ingredient assessment more difficult.

Learn more: Proprietary blends vs. transparent pre-workout formulas and FDA supplement-labeling guidance. [22]

Rhodiola rosea

Definition: A botanical whose root extracts are commonly marketed as adaptogens—substances proposed to help the body respond to stress.

Purpose: Included in some formulas targeting fatigue, perceived effort, or stress-related performance.

Evidence caveat: Evidence remains limited and varies across extracts and study designs. Extract weight alone does not establish equivalence to a researched preparation; standardization and composition matter. “Adaptogen” does not guarantee a meaningful benefit.

Learn more: NCCIH: Rhodiola—usefulness and safety. [23]

Serving size

Definition: The amount of product identified as one serving on the Supplement Facts panel, often expressed in grams and a scoop measure.

Purpose: Provides the basis for interpreting ingredient amounts and servings per container.

Evidence caveat: One scoop is not always one serving. Check the specific label before comparing formulas. Taking more powder increases every ingredient, and scoop volume can be less consistent than weighing the labeled amount.

Learn more: FDA: Supplement Facts and serving-size labeling. [22]

Stevia and steviol glycosides

Definition: Steviol glycosides are intensely sweet compounds obtained from stevia leaves and used in purified sweetener preparations.

Purpose: Provide sweetness with little or no meaningful calorie contribution at typical use levels.

Evidence caveat: Stevia is a sweetener, rather than a performance ingredient. “Plant-derived” does not establish that a complete formula is safer or more effective. FDA's treatment of certain high-purity steviol glycosides differs from its treatment of whole-leaf stevia and crude extracts.

Learn more: FDA: Sweeteners, including stevia-derived substances. [24]

Stimulant-free pre-workout

Definition: A product marketed as excluding stimulant ingredients. It may contain ingredients such as citrulline, creatine, or electrolytes.

Purpose: Offers an option for people who prefer to avoid stimulant exposure.

Evidence caveat: Check the complete formula: “caffeine-free” and “stimulant-free” do not necessarily convey identical information. Removing caffeine does not establish the remaining ingredients' effectiveness or eliminate all possible side effects and interactions.

Learn more: NIH: Exercise supplements and safety considerations. [1]

Sucralose

Definition: A high-intensity artificial sweetener used in some flavored supplements and foods.

Purpose: Provides sweetness with little or no meaningful calorie contribution at typical use levels.

Evidence caveat: Sucralose does not provide a workout-performance benefit. Its presence or absence does not, by itself, determine overall formula quality. FDA permits its use under approved conditions; choosing to avoid it is a separate consideration from judging stimulant doses and performance ingredients.

Learn more: Pre-workout without sucralose: what to look for and FDA information on sweeteners. [24]

Taurine

Definition: An amino sulfonic acid involved in several physiological functions, including cellular fluid regulation and calcium handling.

Purpose: Investigated for endurance, fatigue, recovery, and other exercise outcomes.

Evidence caveat: Some studies report benefits, but results vary across doses, protocols, and exercise tests. Taurine is not caffeine. Research on taurine alone also cannot establish the effects of an energy drink or pre-workout containing multiple ingredients.

Learn more: Review of taurine in sports and exercise. [25]

Tyrosine (L-tyrosine)

Definition: An amino acid used to make catecholamine neurotransmitters, including dopamine and norepinephrine.

Purpose: Marketed for focus and cognitive performance under demanding conditions.

Evidence caveat: Research is most relevant to certain stressful situations, rather than a reliable everyday focus boost. Evidence does not establish consistent improvements in ordinary gym performance, and the available studies have important limitations.

Learn more: Evidence assessment of tyrosine under physical and psychological stress. [26, 27]

Vitamin B12

Definition: A vitamin required for normal red-blood-cell formation, neurological function, and DNA synthesis. Supplemental forms include methylcobalamin and cyanocobalamin.

Purpose: Supports normal nutrient function and is often included in products marketed for energy.

Evidence caveat: Correcting a deficiency matters, but additional B12 does not appear to improve athletic performance or endurance in people with sufficient status. A large percentage of Daily Value is not a measure of stimulant strength or immediate energy.

Learn more: NIH: Vitamin B12 and the evidence on energy and endurance. [28]

How to use this glossary when reading a label

Start with five questions:

1. What is the full serving? Check grams, scoops, and amounts per serving.
2. What form is listed? For example, pure L-citrulline and citrulline malate require different comparisons.
3. How much stimulant exposure does it add? Include caffeine consumed elsewhere that day.
4. Does the ingredient require consistent supplementation? A single pre-workout serving and a multiweek research protocol are different exposures.
5. What outcome was actually studied? An attention test, blood marker, repetition test, and long-term strength gain answer different questions.

For product quality, distinguish label transparency from independent verification. A disclosed formula is easier to assess, but the label alone cannot verify its contents. Athletes subject to drug testing should check appropriate sport-specific certification; certification reduces risk without eliminating it. [14, 15]

How these terms apply to 4 Gauge

The Supplement Facts panel currently displayed for 4 Gauge Pre-Workout identifies one serving as 10 g, or one scoop.

The displayed label includes stevia among the other ingredients and does not list beta-alanine or sucralose. Individual dietary-ingredient amounts are disclosed. [29]

Three distinctions help interpret this formula:

• 6,000 mg citrulline malate is a combined ingredient weight. It should not be described as 6,000 mg pure L-citrulline.
• 1,000 mg creatine contributes to daily intake. It is below the commonly studied maintenance intake of 3–5 g per day.
• 300 mg red beet root does not establish a nitrate dose. The displayed label does not provide a standardized nitrate amount. [29, 10, 1]

These are label facts and research comparisons, rather than clinical proof of the complete formula's effects.

View the current 4 Gauge formula and Supplement Facts panel.

Frequently asked questions

Which pre-workout ingredients have the strongest evidence?

Among common ingredients, caffeine and creatine monohydrate have substantial supporting evidence for specific exercise outcomes. Beta-alanine also has evidence for certain high-intensity tasks when taken consistently. Their benefits are different, and none is necessary for every person or workout. [7, 10, 5]

Does tingling mean a pre-workout is working?

Tingling can indicate a sensory response to beta-alanine, but it does not measure a performance benefit. Beta-alanine's exercise mechanism involves increasing muscle carnosine through consistent supplementation. [5]

Are L-citrulline and citrulline malate interchangeable?

They are related ingredients, but their gram amounts are not interchangeable. Citrulline malate includes malate, so its combined weight is greater than the weight of citrulline alone. Check the listed form and ratio before comparing products. [9]

Is beetroot powder the same as a standardized nitrate supplement?

No. Beetroot can supply nitrate, but the nitrate concentration varies. A stated beetroot-powder weight cannot establish equivalence to a researched product with a measured nitrate dose. [1]

Does L-theanine cancel out caffeine?

No. Research suggests potential benefits for some attention outcomes, but L-theanine does not make caffeine exposure irrelevant or guarantee freedom from side effects. Caffeine amount, timing, sensitivity, and total daily intake still matter. [17, 8]

Does every pre-workout need all these ingredients?

No. This glossary explains terms; it is not a checklist for the longest possible formula. More ingredients do not establish better performance, and research on individual ingredients cannot predict every combination's effects. [1]

Explore related guides

• How much caffeine should be in pre-workout?
• Why does pre-workout make you tingle?
• Pre-workout side effects: causes and what to do
• Proprietary blends vs. fully disclosed formulas
• The 4 Gauge Research Hub

Sources

Source numbers in the text above link to this list. Sources support different kinds of claims: consensus statements, systematic reviews, official fact sheets, and brand-owned label information. Research on individual ingredients does not establish the effects of any finished product. Source list prepared October 2, 2026.

1. NIH Office of Dietary Supplements. Dietary Supplements for Exercise and Athletic Performance, Health Professional Fact Sheet. View source.
2. NIH Office of Dietary Supplements. Carnitine, Health Professional Fact Sheet. View source.
3. Viribay et al. Effects of Arginine Supplementation on Athletic Performance Based on Energy Metabolism: A Systematic Review and Meta-Analysis (2020). View source.
4. Safety and performance benefits of arginine supplements for military personnel: a systematic review (2016). View source.
5. Trexler et al. International Society of Sports Nutrition position stand: Beta-Alanine (2015). View source.
6. Zawieja et al. Effects of chronic betaine supplementation on exercise performance: Systematic review and meta-analysis (2024). View source.
7. Guest et al. International society of sports nutrition position stand: caffeine and exercise performance (2021). View source.
8. FDA. Spilling the Beans: How Much Caffeine is Too Much? View source.
9. Gough et al. A critical review of citrulline malate supplementation and exercise performance (2021). View source.
10. Kreider et al. International Society of Sports Nutrition position stand: safety and efficacy of creatine supplementation in exercise, sport, and medicine (2017). View source.
11. Kalman et al. Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men (2012). View source.
12. ISSN position stand on essential amino acid supplementation (2023). View source.
13. Sawka et al. American College of Sports Medicine position stand. Exercise and fluid replacement (2007). View source.
14. FDA. Questions and Answers on Dietary Supplements. View source.
15. USADA. Supplement Risk and NSF Certified for Sport. View source.
16. The Effect of Pre-Exercise Hyperhydration on Exercise Performance, Physiological Outcomes and Gastrointestinal Symptoms: A Systematic Review (2023). View source.
17. Payne et al. Effects of Tea or its Bioactive Compounds L-Theanine or L-Theanine plus Caffeine on Cognition, Sleep, and Mood in Healthy Participants: A Systematic Review and Meta-Analysis of Randomized Controlled Trials (2025). View source.
18. NIH Office of Dietary Supplements. Magnesium, Health Professional Fact Sheet. View source.
19. The effect of magnesium supplementation on muscle fitness: a meta-analysis and systematic review (2018). View source.
20. NIH Office of Dietary Supplements. Niacin, Health Professional Fact Sheet. View source.
21. Factors that Moderate the Effect of Nitrate Ingestion on Exercise Performance in Adults: A Systematic Review with Meta-Analyses and Meta-Regressions (2022). View source.
22. FDA. Dietary Supplement Labeling Guide: Chapter IV. Nutrition Labeling. View source.
23. NCCIH. Rhodiola: Usefulness and Safety. View source.
24. FDA. Aspartame and Other Sweeteners in Food. View source.
25. Taurine in sports and exercise (2021). View source.
26. Tyrosine for Mitigating Stress and Enhancing Performance in Healthy Adult Humans, a Rapid Evidence Assessment of the Literature (2015). View source.
27. Behavioral and cognitive effects of tyrosine intake in healthy human adults (2015). View source.
28. NIH Office of Dietary Supplements. Vitamin B12, Health Professional Fact Sheet. View source.
29. 4 Gauge. 4 Gauge Pre-Workout: current Supplement Facts panel. Product page (label image). Brand-owned source for composition only; not independent efficacy evidence. Panel inspected on the product page October 2, 2026.

This glossary is educational and does not replace individual medical advice. Supplements can interact with medications and may not be appropriate for everyone.