Side effects of Theacrine

Theacrine is sold as a “mild” stimulant without tolerance and without blood-pressure spikes. Short-term studies do indeed show fairly good tolerability, but this does not mean there are no side effects at all. The editorial team gathered data on which adverse reactions are possible, what they depend on and how to distinguish mild discomfort from an alarming signal.

What safety studies show

The most detailed safety assessment of theacrine was carried out by Taylor et al. (2016). Healthy adults took 200 or 300 mg of theacrine or placebo daily for eight weeks. The authors assessed heart rate, blood pressure, blood biochemistry, liver and kidney function, the lipid profile and hematology.

According to the results, no clinically significant differences from placebo were found in these indicators. Nor were signs of tolerance, characteristic of regular caffeine consumption, recorded. These data formed the basis of the marketing claim of a “safe stimulant.”

Ziegenfuss et al. (2017) also observed no significant changes in heart rate and blood pressure after taking theacrine, unlike the typical reaction to caffeine in people without tolerance.

At the same time, it is important to remember the limitations: an eight-week study with a limited number of healthy participants cannot detect rare reactions or the consequences of many years of use. The experience of using theacrine is far shorter and narrower than that of caffeine.

The most frequent adverse effects

Since theacrine acts through the adenosine and, according to animal data, dopamine systems, its possible side effects are similar to those of other stimulants. Users most often report difficulty falling asleep, especially when taken in the second half of the day. This is explained by the substance's long stay in the body.

The second group is nervousness, irritability, a feeling of inner tension. They more often arise when combined with caffeine or other stimulants in pre-workout complexes.

The third is headache and dizziness. They may be related both to the substance itself and to insufficient water intake, skipping meals or a sharp change in the usual amount of caffeine.

The fourth is gastrointestinal symptoms: nausea, stomach discomfort, especially when taken on an empty stomach. In most cases they pass after taking it with food or reducing the amount.

Interaction with caffeine and total stimulant load

In real life theacrine is rarely taken in isolation. Most pre-workout complexes and energy products combine it with caffeine, and often with other stimulants as well: synephrine, yohimbine, methylliberine, guarana extracts.

He et al. (2017) showed that when taken together with caffeine, the exposure to theacrine increases. That is, caffeine slows the elimination of theacrine, and its effect lasts longer than with isolated intake. For sleep and the nervous system this is practically important.

Caffeine itself has well-described side effects: tachycardia, anxiety, insomnia, increased blood pressure. EFSA considers a caffeine intake of up to 400 mg per day from all sources and up to 200 mg per single intake safe for healthy adults. Theacrine adds to this load, and the safety limits for the combination have not been established.

Therefore the risk should be assessed not by a single substance but by everything a person consumes during the day: coffee, energy drinks, pre-workout complexes, fat burners. It is precisely the total stimulant load that most often becomes the cause of unpleasant reactions.

Who is more vulnerable

People with cardiovascular diseases, in particular with arrhythmias, uncontrolled hypertension or coronary heart disease, have a higher risk of complications from any stimulants. The neutral indicators in studies on healthy young people cannot be transferred to this group.

People with anxiety disorders, panic attacks or insomnia may react to theacrine with intensified symptoms. The effect on the dopamine system may theoretically also be significant for people with bipolar disorder.

Pregnant and breastfeeding women, children and adolescents are groups for which there are no data on the safety of theacrine at all. For caffeine there are separate restrictions during pregnancy, and it is logical to extend caution to related substances.

Also vulnerable are people taking medications that affect heart rhythm, blood pressure, the nervous system, as well as drugs whose metabolism may intersect with the metabolism of methylxanthines. We write about the contraindications in more detail in a separate article.

How to reduce the risk and when to see a doctor

The first rule is transparency of the composition. Choose products that clearly state the amount of theacrine and caffeine per serving, and avoid “proprietary blends” with an unknown content of stimulants.

The second is accounting for the total load. Take into account coffee, tea, energy drinks and other supplements. If you already consume a lot of caffeine, adding theacrine increases the risk of adverse reactions.

The third is taking it in the first half of the day. Because of the long action, late intake substantially increases the risk of sleep disturbances, and lack of sleep in itself worsens recovery and results.

You should seek medical help immediately in case of chest pain, pronounced palpitations or interruptions in the heart's work, shortness of breath, fainting, severe headache or signs of an allergic reaction. In such cases intake must be stopped.

• Start with the minimum amount and assess the reaction.
• Do not combine several stimulating products in one day.
• Do not take theacrine later than midday.
• Stop taking it at any alarming symptoms from the heart.

Editorial conclusions

Short-term studies show that theacrine, at the doses studied, is well tolerated by healthy adults and does not substantially change pulse, blood pressure or laboratory indicators.

At the same time, effects typical of stimulants are possible: insomnia, nervousness, headache, stomach discomfort. The risk increases when combined with caffeine and other stimulants because of the prolongation of theacrine's action.

Long-term data and data for vulnerable groups are absent, so a “safe stimulant” is a conclusion for a limited population, not for everyone.

We also recommend reading “Who should not take Theacrine,” “How to take Theacrine: dosage, timing, duration” and “Theacrine: dosage forms and which to choose.”

References

1. Taylor L, Mumford P, Roberts M, et al. Safety of TeaCrine®, a non-habituating, naturally-occurring purine alkaloid over eight weeks of continuous use. J Int Soc Sports Nutr. 2016;13:2.
2. Ziegenfuss TN, Habowski SM, Sandrock JE, et al. A two-part approach to examine the effects of theacrine (TeaCrine®) supplementation on oxygen consumption, hemodynamic responses, and subjective measures of cognitive and psychometric parameters. J Diet Suppl. 2017;14(1):9–24.
3. He H, Ma D, Crone LB, et al. Assessment of the drug–drug interaction potential between theacrine and caffeine in humans. J Caffeine Res. 2017;7(3):95–102.
4. EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Scientific opinion on the safety of caffeine. EFSA J. 2015;13(5):4102.
5. Feduccia AA, Wang Y, Simms JA, et al. Locomotor activation by theacrine, a purine alkaloid structurally similar to caffeine: involvement of adenosine and dopamine receptors. Pharmacol Biochem Behav. 2012;102(2):241–248.
6. Guest NS, VanDusseldorp TA, Nelson MT, et al. International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr. 2021;18(1):1.