Abstract13C-based metabolic flux analysis is an excellent technique to resolve fluxes in the central carbon metabolism but costs can be significant when using specialized tracers. This work presents a framework for cost-effective design of 13 C-tracer experiments, illustrated on two different networks.Linear and non-linear optimal input mixtures are computed for networks high amounts of 1,2-13 C 2 glucose combined with uniformly labelled glucose.Experimental designs are evaluated based on a linear (D-criterion) and nonlinear approach (S-criterion). Both approaches generate almost the same input mixture, however, the linear approach is favoured due to its low computational effort. The high amount of 1,2-13 C 2 glucose in the optimal designs coincides with a high experimental cost, which is further enhanced when la-