Lithium is the gold-standard treatment for bipolar disorder, which impacts over 5.7 million US adults. Yet, this treatment has a narrow therapeutic range that is dangerously close to toxic levels. Though extended-release lithium formulations exist, they necessitate frequent serum monitoring and cause adverse effects in nearly one in ten patients. Here, we report a novel lithium formulation with improved release kinetics. By coating alginate microparticles with lithium-doped metal phenolic networks (MPNs), lithium release is maintained within a safe, therapeutically relevant range for an unprecedented 100 hours. Release studies show lithium concentrations reaching their peak in serum after 11 hours, more than twice as long as existing formulations, with maintenance of therapeutic levels for at least four days. This novel lithium formulation is the first to offer such tight control over lithium concentration in serum for such an extended time, providing the potential to revolutionize lithium therapy and vastly improve patient experience with this medication.