Guarana

Paullinia cupana

Snapshot

Indications	Contraindications
Fatigue (traditional use)¹ Attention and processing speed² Reaction time² Appetite suppression³ Cancer-related anorexia⁴	Hypertension¹ Arrhythmias¹ Gastric or duodenal ulcers¹ Hyperthyroidism¹

Guarana (Paullinia cupana) is the seed of an Amazonian plant that contains caffeine and caffeine-like compounds³. Its effects are attributed largely to caffeine's central nervous system stimulation³. It is taken for energy, fatigue, appetite suppression, and sexual performance³. The European Medicines Agency monograph recognizes traditional use for fatigue and weakness¹.

Acute guarana ingestion produced a small gain in response time without a change in accuracy in a meta-analysis of placebo-controlled studies. For cancer-related fatigue, a meta-analysis found guarana no better than placebo, with very low-quality evidence⁵. In cell and earthworm models and in blood cells from patients with Parkinson's disease, a 2025 laboratory study of a guarana and cocoa husk extract found lower inflammatory cytokine levels; no clinical trial has tested it. Products listing guarana number over one thousand, mainly capsules, tablets, powders, and teas; see Form comparison.

The most consequential caution is cardiovascular.^{1, 3} The European Medicines Agency monograph lists hypertension and arrhythmias as contraindications¹, and case reports describe tachycardia and premature ventricular contractions after guarana³. Per Memorial Sloan Kettering, patients taking other stimulants or warfarin are directed to discuss guarana with their healthcare provider, given its stimulant load and antiplatelet activity in laboratory studies³.

Last updated October 16, 2026. Read how we make monographs.

In the full monograph

52 sources, 44 studies

When to useThe situations practitioners use it for, each with the reason and the study behind it.
SafetyWho should avoid it, who needs extra care, and the side effects reported in studies.
InteractionsThe medicines and supplements it interacts with, the effect of each, and what labeling says to watch.
Protocol notesThe doses used in studies, how and when they were taken, and how the forms on the market compare.
How it worksWhat it is and how it works in the body, in plain terms.
Published studiesThe studies behind each use, popular claims checked against them, and trials still under way.
Word of mouthWhat patients and practitioners report online, kept separate from the clinical evidence.
Clinical perspectiveA closing read of where the evidence is solid, where it is thin, and what has not been studied.

Snapshot

In the full monograph

Sources