Wegovy starts working in the body within a few days after the first injection, with the medication reaching peak concentration in one to three days. However, the noticeable effects on appetite and weight loss typically take several weeks to manifest because the dosage is started low (0.25 mg/week) and gradually increased over about 16 to 20 weeks to the maintenance dose (usually 2.4 mg/week). Many people begin to see initial weight loss within the first few weeks, averaging about 2% to 3% of total body weight lost in the first month. More significant and sustained weight loss, such as 10% or more of body weight, tends to occur over several months as the dose reaches the maintenance level and with ongoing lifestyle changes like diet and exercise. The effect on appetite can also take a few days to weeks to become noticeable. In summary, Wegovy starts working quickly in the body, but noticeable weight loss usually begins within a month and improves over several months of treatment with dose escalation and lifestyle changes.