Does Guarana Have Side Effects? The Honest Evidence

For most healthy adults, guarana does not cause harm when consumed at usual doses. The key point is this: guarana is mainly a natural source of caffeine, and it is the caffeine — not the plant itself — that explains both the desired effects (alertness, focus) and the unwanted ones (insomnia, nervousness, palpitations). What matters, therefore, is not guarana in isolation, but the total caffeine you take in per day, adding up coffee, tea, soft drinks, chocolate and supplements.

There are, however, groups for whom guarana is not advised or requires caution: pregnant and breastfeeding women, children, people with heart conditions, anxiety or caffeine sensitivity, and those taking certain medicines. This article explains what the evidence shows, where the limits are and how to decide safely.

Is guarana dangerous in itself, or is it the caffeine?

Guarana (Paullinia cupana) is a plant from the Amazon whose seeds are rich in methylxanthines — mainly caffeine — and flavonoids. A narrative review on guarana consumption and human health describes precisely these bioactive compounds as responsible for the effects studied, and notes that the available evidence still lacks more human studies and mechanistic research ¹.

In other words: when you assess the safety of guarana, you are essentially assessing the safety of the caffeine it provides. A comprehensive review on caffeine in food describes it as one of the most widely consumed dietary ingredients in the world, present in coffee beans, cocoa, kola nuts, guarana berries and tea leaves, and considers moderate consumption to be safe, with attributed benefits such as reduced fatigue and increased alertness — but stresses that the negative effects of excessive consumption must be taken into account, particularly in children and pregnant women ².

Who should avoid guarana?

There are groups for whom guarana is not the right choice. If you fall into any of these categories, talk to a healthcare professional before consuming it.

• Pregnant and breastfeeding women: reviews on caffeine in food stress that the negative effects of excessive consumption must be taken into account, particularly in pregnant women ². As guarana contributes to your total caffeine for the day, it can easily push your intake beyond what is desirable if added to coffee or tea.
• Children: the review on caffeine in food stresses that the negative effects of excessive consumption must be taken into account, particularly in children ². There is no evidence of benefit that justifies the exposure.
• People with heart conditions or uncontrolled hypertension: caffeine has haemodynamic effects. In a randomised, double-blind, crossover trial with 16 healthy adults, taking supplements containing guarana (in combination with ephedra) significantly increased heart rate (maximum increase of 9.4 ± 8.6 beats/min) and blood pressure (maximum increase of 11.5 ± 10.7 mmHg systolic and 7.3 ± 7.4 mmHg diastolic) compared with placebo ³. It is important to note that this study used a combination with ephedra, so it does not isolate the effect of guarana — but it shows that stimulants of this type have a measurable cardiovascular impact.
• Anyone taking regular medication: caffeine can interact with various medicines. If you take medicines for the heart, blood pressure, anxiety or depression, talk to your doctor or pharmacist first — see the article on guarana and medications.

What does the evidence say about guarana's effects?

The specific evidence on guarana as a whole plant is more limited than the evidence on caffeine. A 2023 meta-analysis, which pooled eight placebo-controlled studies with 328 participants, assessed the acute effect of guarana on cognitive performance. The doses studied ranged from 37.5 mg to 500 mg of guarana, with a reported caffeine content of between 4.3 mg and 100 mg. The overall mean effect was less than trivial (Hedge's g = 0.076; p = 0.14), but a subgroup analysis found a small but significant effect on reaction time in favour of guarana versus placebo (g = 0.202; p = 0.005), with no difference in accuracy measures ⁴.

This means that the evidence for cognitive improvements with guarana is modest and not uniform. For a more detailed analysis, see guarana benefits: what the science really shows and how guarana works.

Does guarana help with weight loss?

This is one of the most common claims — and one of the weakest. A systematic review on adverse events of herbal weight-loss supplements assessed several plants, including Paullinia cupana, and concluded that adverse events, some serious, are reported with the use of some of these supplements; for supplements containing ephedra and ephedrine, an increased risk of psychiatric, autonomic or gastrointestinal events and palpitations was identified ⁵.

In addition, a randomised, double-blind trial with 67 overweight adults, which tested an herbal supplement containing Ma Huang and guarana for 8 weeks, observed greater weight loss and fat mass loss in the active group — but 8 of the 35 participants in the active group (23%) dropped out of the study due to effects potentially related to the treatment, with dry mouth, insomnia and headache being the most frequent symptoms ⁶. Note that this study combined guarana with ephedra, so it does not allow the results to be attributed to guarana alone. There is no evidence to support the idea that guarana, on its own, causes significant weight loss.

How much is too much? Signs you have overdone it

The negative effects of excessive caffeine consumption must be taken into account, particularly in children and pregnant women ². The amount that triggers symptoms varies greatly from person to person: some people feel effects at low doses and others tolerate more.

• Nervousness or agitation
• Rapid or irregular heartbeat
• Insomnia
• Headaches
• Dizziness
• Stomach discomfort or nausea
• Anxiety or panic attacks in severe cases

If you feel any of these symptoms, stop consuming caffeine, drink water and rest. In severe cases — fainting, chest pain or a very irregular heartbeat — seek medical help immediately.

What the label of the Energy Gummies with Guarana says

TuttiBear's Energy Gummies with Guarana provide, per serving of 2 gummies: 200 mg of guarana extract, of which 44 mg of caffeine, 200 mg of L-theanine, 100 mg of L-tyrosine, 1.4 mg of vitamin B6 (100% NRV), 10 µg of vitamin B12 (400% NRV) and 40 mg of vitamin C (50% NRV). The directions for use state to chew 2 gummies per day, preferably after a meal, without exceeding the recommended daily dose.

Compare with the studies: the meta-analysis on cognition used guarana doses between 37.5 mg and 500 mg, with 4.3 mg to 100 mg of caffeine ⁴. The gummies provide 200 mg of extract and 44 mg of caffeine per serving — within the range studied, but remember that study doses are not dosing instructions and that each product has its own directions for use.

The label warnings are clear: contains caffeine (44 mg per daily dose); not recommended for children, pregnant or breastfeeding women; contains polyols, whose excessive consumption may have a laxative effect; and, in case of illness or when taking medicines, you should consult a healthcare professional before consuming it.

As for the vitamins, vitamin C contributes to the normal function of the immune system and vitamin B6 contributes to the normal functioning of the nervous system, under the claims authorised in Regulation (EU) No 432/2012 ⁷.

How to use guarana safely

If you decide to use guarana, these practical rules help reduce risks:

• Respect the dose on the label. More is not better.
• Count your total caffeine for the day. Add guarana to the coffee, tea, soft drinks and chocolate you consume.
• Avoid it late in the day. Caffeine can interfere with sleep; for many people, it is best taken up to early afternoon. See guarana: when to take it.
• Do not combine it with other stimulants. Avoid energy drinks or other caffeine supplements on the same day.
• Consider breaks. Continued daily consumption can lead to tolerance and, when you stop abruptly, to headaches and fatigue.

To better understand how to read the label and calculate your dose, see guarana daily dose.

Guarana in pregnancy: what to know

Pregnancy is the case where caution is most evident. Reviews on caffeine in food stress that the negative effects of excessive consumption must be taken into account, particularly in pregnant women ². As guarana is a source of caffeine, it contributes to the daily total. If you are pregnant or breastfeeding, talk to your doctor before consuming any supplement with guarana — see also guarana in pregnancy.

Official recommendations indicate that pregnant women should not exceed 200 mg of caffeine per day, from all sources. As guarana contributes to that total, it is easy to go over the limit without realising, especially if you also drink coffee or tea.

When to talk to a healthcare professional

If you have any medical condition, take medication regularly, are pregnant or breastfeeding, or simply are not sure whether guarana is suitable for you, the recommendation is always the same: talk to a doctor or pharmacist. Only someone who knows your medical history can assess the individual risk. Guarana is not a medicine — it is a food — and, like any food, it can be beneficial or harmful depending on who consumes it and in what amount. For most healthy adults, with no contraindications and respecting the doses, it is probably safe. If in doubt, do not take the risk.

If you still have doubts, the best thing really is to ask a healthcare professional — there is no shame in that at all. A pharmacist can help you understand whether guarana is suitable for you, taking into account your health and the medication you take, and a doctor can assess your individual case.

Frequently asked questions

Is guarana bad for the liver?

There is no evidence that guarana, on its own, causes liver damage at usual doses. A systematic review on adverse events of herbal weight-loss supplements reported cases of liver injury with some supplements, but those cases were mainly associated with products containing ephedra or combinations of multiple ingredients, not guarana alone. If you have liver disease, talk to your doctor before consuming it.

Can I take guarana every day?

For most healthy adults, daily consumption within caffeine limits is generally considered safe. However, continued consumption can lead to tolerance and, when you stop suddenly, to headaches and fatigue. Many people choose to take breaks or alternate with caffeine-free days. Always respect the dose stated on the product label.

How much caffeine does guarana contain?

The caffeine content of guarana varies with the concentration of the extract. In TuttiBear's Energy Gummies with Guarana, each serving of 2 gummies provides 200 mg of guarana extract, of which 44 mg of caffeine. In the meta-analysis on cognition, the guarana doses studied ranged from 37.5 mg to 500 mg, with a reported caffeine content of between 4.3 mg and 100 mg.

Does guarana interact with medications?

Yes, caffeine can interact with various medicines, including some used for the heart, blood pressure, anxiety and depression. If you take regular medication, talk to your doctor or pharmacist before consuming guarana. The label of the Energy Gummies with Guarana also states that, in case of illness or when taking medicines, you should consult a healthcare professional.

Is guarana addictive?

Caffeine can create mild physical dependence. If you consume guarana daily and stop suddenly, you may feel headaches, fatigue and irritability for a few days. It is not dependence in the classic sense associated with heavy drugs, and most people can reduce gradually without much difficulty.

Can children take guarana?

It is not recommended. The review on caffeine in food stresses that the negative effects of excessive consumption must be taken into account, particularly in children. In addition, the label of TuttiBear's Energy Gummies with Guarana explicitly states that they are not recommended for children. There is no evidence of benefit that justifies exposing children to caffeine through supplements.