Pre-Workout and Energy Drink Amino Acid Blends: Taurine, Caffeine, Citrulline and Proprietary Blend Risks
What the sources say about pre-workout and energy drink blends: caffeine, taurine, citrulline, proprietary blends, banned stimulants like DMAA, and who should avoid them.
Content last updated . This page has not been medically reviewed.
Get care first if you see these signs
Chest pain, fainting, a racing or irregular heartbeat, a seizure or severe shortness of breath after a stimulant product need urgent medical care: call 911 (US). The FDA warns that DMAA, a stimulant found in some sports products, can lead to cardiovascular problems such as shortness of breath, arrhythmias, tightening in the chest and heart attack, as well as seizures. [1] If a child may have swallowed a product, call Poison Help at 1-800-222-1222 (US). See Poisoning: what to do first.What is in these products
Pre-workout powders and energy drinks are mixtures. A 2023 sports nutrition position stand lists the usual contents of energy drinks as caffeine, taurine, ginseng, guarana, carnitine, choline and more. [2] The same stand says the primary ergogenic nutrients in most energy drinks and shots, based on scientific evidence, appear to be caffeine and/or the carbohydrate provision, and that many ingredients have not been studied alone or in combination. [2] That is a statement about performance, not safety. Our reading is that the amino acid ingredients in a blend are not its best-supported part.Evidence labels used here: documented (a regulator or position statement says so), limited (small studies or surveys), Proper evidence not found.
Ingredient table
| Ingredient | What the sources we read say | Label |
|---|---|---|
| Caffeine | The FDA has cited 400 milligrams a day as an amount not generally associated with negative effects for most adults, with wide variation in sensitivity, and says too much can have negative effects. [3] It also notes caffeine can be an added ingredient in protein bars, dietary supplements and over-the-counter medicines. [3] See Caffeine supplements. | Documented |
| Taurine | EFSA's 2009 opinion concluded exposure to taurine and d-glucuronolactone at energy-drink levels is not a safety concern, and linked reported problems to the well-known side effects of high caffeine intake. [4] The page carries a notice that it is over 10 years old. [4] See Taurine, energy drinks and heart health. | Documented (older opinion) |
| Citrulline | A 4-week trial in 60 healthy men reported no treatment-related adverse events at the amounts tested; the authors worked for supplement-ingredient companies. [5] Interactions with blood pressure medicines: Proper evidence not found. See Amino acid supplement and medicine interactions. | Limited |
| Beta-alanine | The only reported side effect in the ISSN position stand is paraesthesia (tingling). [6] See Beta-alanine. | Documented |
| Tyrosine, carnitine, L-theanine | Listed by the position stand as common energy drink ingredients. [2] Their safety in combinations: Proper evidence not found. See Tyrosine, Carnitine and L-theanine. | Proper evidence not found |
| DMAA (methylhexanamine) | The FDA says DMAA-containing products marketed as dietary supplements are illegal and their marketing violates the law, and advises consumers not to use them. [1] It can raise blood pressure. [1] DMAA can be listed under other names, including methylhexanamine. [1] | Documented harm |
Proprietary blends: why the label may not tell you the amounts
The FDA's labeling guide describes how a "proprietary blend" is shown: the blend's name, the total weight of the "other dietary ingredients" in it, and the ingredients listed in descending order of predominance by weight. [7] The page we read does not say each such ingredient's amount must be declared separately. If a label shows only a blend total, you cannot tell how much of any one ingredient, such as caffeine, you are getting. A survey of regular users also noted potentially significant variability in the caffeine content of products. [8] The FDA says it has no regulation specific to "energy drinks"; the general ingredient safety rules apply. [3] See Reading an amino acid supplement label and Reading supplement labels.What users report
In an online survey of 872 regular users of multi-ingredient pre-workout products, over half (54%) reported side effects including skin reactions, heart abnormalities and nausea. [8] This is self-reported, from social-media recruitment, and does not show cause. It does show that side effects are common enough in users to take seriously. A review of energy drinks in young people likewise concluded they have no therapeutic benefit and that many ingredients are understudied and not regulated. [9]Who should avoid or ask first
- Children and teens. The American Academy of Pediatrics (2011) concluded that caffeine and other stimulants in energy drinks have no place in the diet of children and adolescents. [10] The FDA says medical experts advise against energy drinks for children and teens. [3]
- Pregnancy, trying to conceive, breastfeeding, and caffeine sensitivity. The 2023 position stand does not recommend energy drinks or shots for these groups. [2] The FDA recommends talking to a health care provider about limiting caffeine if you are pregnant, trying to become pregnant or breastfeeding. [3]
- Heart, metabolic, liver, kidney or neurologic disease, diabetes, and people on medicines. The position stand says people with diabetes or preexisting cardiovascular, metabolic, hepatorenal or neurologic disease who take medicines that may be affected by caffeine or other stimulants should consult a physician first. [2] See Medication interactions.
- Anyone before surgery. See Supplements before surgery.
Contamination and banned substances
Product quality varies and "natural" does not mean safe. [11] Athletes who are tested should read Sports certification and banned-substance contamination. General quality guidance is on Quality testing and certifications and Product quality and contamination. For multi-ingredient "brain" products, see Nootropic safety and claim checks.Reporting
In the US, anyone can report an adverse event thought to be related to a dietary supplement to the FDA. [12]Frequently asked questions
Is pre-workout safe?
It depends on the product, your health and medicines, and the amounts of caffeine and other ingredients, which may not be fully listed. The sources we read call for caution in children, pregnancy and heart or other chronic conditions. [2][3] Ask a clinician or pharmacist if unsure.
Is taurine in energy drinks dangerous?
EFSA's 2009 opinion found taurine exposure at energy-drink levels not a safety concern, and tied reported problems to caffeine. [4] The opinion is over 10 years old, and newer sources are on the taurine page linked above.
What is a proprietary blend?
A labeling term. The FDA describes it as a named blend with a total weight and ingredients in descending order by weight. [7] It may not reveal each ingredient's amount.
What is DMAA?
A stimulant that the FDA says is not a legal dietary ingredient. It says DMAA can raise blood pressure and cause cardiovascular problems. [1]
Can teenagers use pre-workout or energy drinks?
Pediatric and FDA sources advise against energy drinks for children and teens. [10][3]
References
- US Food and Drug Administration, DMAA in Products Marketed as Dietary Supplements (page dated August 2018). Read 2026-10-23.
- Jagim AR et al. International society of sports nutrition position stand: energy drinks and energy shots. J Int Soc Sports Nutr 2023. Read 2026-10-23.
- US Food and Drug Administration, Spilling the Beans: How Much Caffeine Is Too Much?. Read 2026-10-23.
- European Food Safety Authority, EFSA adopts opinion on two ingredients commonly used in some energy drinks, 12 February 2009 (the page carries a notice that it is over 10 years old). Read 2026-10-23.
- Miura N et al. Subchronic tolerance trials of graded oral supplementation with ornithine hydrochloride or citrulline in healthy adults. Amino Acids 2023 (authors employed by supplement-ingredient companies). Read 2026-10-23.
- Trexler ET et al. International society of sports nutrition position stand: Beta-Alanine. J Int Soc Sports Nutr 2015. Read 2026-10-23.
- US Food and Drug Administration, Dietary Supplement Labeling Guide: Chapter IV, Nutrition Labeling. Read 2026-10-23.
- Jagim AR, Camic CL, Harty PS. Common Habits, Adverse Events, and Opinions Regarding Pre-Workout Supplement Use Among Regular Consumers. Nutrients 2019 (online self-report survey). Read 2026-10-23.
- Seifert SM et al. Health effects of energy drinks on children, adolescents, and young adults. Pediatrics 2011. Read 2026-10-23.
- American Academy of Pediatrics, Committee on Nutrition and Council on Sports Medicine and Fitness. Sports drinks and energy drinks for children and adolescents: are they appropriate? Pediatrics 2011. Read 2026-10-23.
- US Food and Drug Administration, Mixing Medications and Dietary Supplements Can Endanger Your Health (consumer update, 2022). Read 2026-10-23.
- US Food and Drug Administration, Questions and Answers on Dietary Supplements. Read 2026-10-23.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.