Is it sufficient to confirm with the manufacturer of imported dietary supplements that they are free from animal derivatives and alcohol in order to consume them, or is it a condition that they obtain a halal certificate from an Islamic organization and have that printed on the packaging?

Originally, the report and affirmation of a non-Muslim are accepted in financial dealings but not in matters of religion. Accordingly, it is permissible to rely on a company's report that materials do not contain prohibited substances, and it is not necessary for the materials to have a halal (definition) certificate, unless strong evidence suggests the company is not truthful. Muslims have eaten cheeses from non-Muslims without inquiry. However, if it is certain that a substance is prohibited, consuming it is forbidden. In cases of doubt, it is preferable to abstain, based on the Prophet's (peace be upon him) saying: "Leave that which makes you doubt for that which does not make you doubt."