We have performed and presented a systematic study to improve our understanding of the transport of organic carboxylates. Our findings reveal that carboxylic acids can diffuse freely into liposomes suspended in NaNO3 solutions at pH 7. This is particularly significant as NaNO3 is commonly used to study carboxylate transport in large unilamellar vesicles. This highlights the significance of the effect of the medium during transport experiments, particularly in cellular studies. Furthermore, we found that -OH groups significantly impact carboxylate transport, providing new opportunities to explore other functional groups in organic anions and assess their influence in transport experiments. Our findings shed light on how carboxylates are internalised into liposomes and could contribute to the development of carboxylate-based drugs and our understanding of the transmembrane transport of other biologically relevant organic anions.