Tremfya (guselkumab) and Ilumya (tildrakizumab) are both injectable medications used to treat moderate-to-severe plaque psoriasis, but they have some key differences. Tremfya is also approved for treating active psoriatic arthritis, while Ilumya is not. You can inject Tremfya yourself at home after proper training, but Ilumya must be administered by a healthcare provider. Tremfya is given every 8 weeks after the initial doses, whereas Ilumya is given every 3 months after the first two doses. Both medications can be expensive. Tremfya can take several months to show full effects, with improvements in psoriasis seen after about 4 months and in psoriatic arthritis after about 6 months. Ilumya tends to show improvement in psoriasis plaques after about 3 months, with continued clearing after 7 months. Both medications can raise the risk of infections and have similar side effects, such as upper respiratory infections.