autoadministrarse

To self-administer, most often used for medication (autoadministrarse una inyección) or, more abstractly, for managing one's own resources or affairs (autoadministrarse el tiempo). Frequent in medical and administrative contexts.

• El paciente aprendió a autoadministrarse la insulina. — The patient learned to self-administer insulin.
• La empresa decidió autoadministrarse en lugar de contratar una gestora externa. — The company decided to self-manage instead of hiring an outside firm.
• Se autoadministra el sueldo con mucho cuidado. — He manages his own salary very carefully.

Using autoadministrarse loosely for any kind of self-care — it specifically implies formally giving or managing something (a drug, a budget, an organization), not general self-improvement.