Levothyroxine quality and consistency matters for hypothyroid dogs, with differences between products affecting treatment efficacy and welfare outcomes.
Levothyroxine treatment quality matters for welfare because inconsistent hormone levels cause oscillation between hypothyroid symptoms (when underdosed) and hyperthyroid symptoms (when overdosed). A dog switched between levothyroxine products without monitoring may experience this oscillation as a welfare consequence of a seemingly routine prescription management decision. The welfare-protective approach maintains consistency in product and timing, monitors regularly, and recalculates dosing when body weight changes — small management commitments that sustain the consistent hormone levels that enable sustained welfare improvement.