Subclinical hypocalcemia (SCH) is an invisible threat to both the dairy cow and producer. As nearly 45 percent of multiparous cows experience SCH during the early lactation period, producers can implement dietary strategies such as feeding negative dietary cation anion difference (DCAD) rations in the late dry period or administering prophylactic calcium treatments to fresh cows to minimize the risk of SCH. Although negative DCAD rations have successfully reduced the incidence of clinical milk fever, many cows still experience SCH after calving. For this reason, it is commonplace to administer supplemental calcium at calving to help maintain blood calcium concentrations. Despite the widespread use of oral calcium boluses, their impacts on production and health are variable. Large-scale field studies show that when high-producing or lame cows are given calcium boluses after calving, they produce more milk and experience less disease than cows of similar status not given a bolus. However, low-producing cows and primiparous cows are negatively impacted by calcium bolus administration.