Caffeine-based thermogenic capsules have been used mainly by those who want to stay active longer and/or by people who attend gyms and gyms. This helps to increase energy expenditure, in addition to inducing the release of serotonin and dopamine, due to its ability to bind to adenosine receptors in the brain, leading to mood swings. Caffeine, 1,3,7-trimethylxanthine, is an alkaloid that acts directly on the central nervous system, increasing energy, in addition to decreasing the feeling of tiredness, causing a decrease in physical and mental fatigue. In Brazil, the quality control of these is done by the Health Surveillance Agency - ANVISA through resolution RDC N°18 of 12,010, which indicates that supplements based on this compound must have between 210 and 420 mg per serving. Thus, it is important to develop suitable analytical methodologies for the quality control of these supplements. In this way, this work aims at the qualification and quantification of caffeine in these products using Nuclear Magnetic Resonance acting in the quantitative mode - NMRq . In this study, significant differences were found between the information presented by the manufacturer on the label and the quantification of caffeine found through the assay. Six samples with a content above 115% (samples 1, 2, 4, 6, 7 and 10), three samples with a content below 85% (sample 5, 8 and 9) and one sample that presented a content of 4.34 % of the amount expressed on the label (sample 11). In summary, this article demonstrates the applicability of qNMR using 1 H to determine caffeine content in commercially available thermogenic capsules. It is a fast method, with minimal sample preparation and can be applied both to powder-based products with a high caffeine content and to oil-based products with a lower caffeine content. [resumo fornecido pelo autor]