Blood plasma and serum are among the most common biofluids studied by metabolomics. The plethora of collection tubes available and variety of coatings on offer make it difficult to decide which collection tube offers the greatest reproducibility and least signal interference for metabolomics studies. We have acquired the NMR proton spectra of water washes of a range of monovettes available to the UK National Health Service (NHS) clinicians in order to demonstrate the variability between tubes, including different batches of the same type. This technical note provides clear evidence that sample collection tubes should be tested before selecting the most appropriate one for NMR metabolomic studies. From the collection tubes tested in this study we found Serum Z blood collection tube most suited to NMR metabolomics both in residual signals arising and also variance between batches.