A method for gram-scale production of isotopically labeled hydrogen peroxide was developed. Although successful use of the product was limited by its purity, concentration, and label incorporation, labeling experiments were successfully performed on two uranyl peroxide materials, studtite and Li@U28. These experiments confirmed peak assignments of studtite and challenged those of the UPC, indicating errors and unrecognized complexity in the traditional assignments. Based on these examples, the potential benefit of future labeling work is strongly indicated.