Taking 20 mg tadalafil without a prescription is illegal and dangerous in most countries.

1. Legal reasons

Tadalafil is a medicine used to treat erectile dysfunction and other related urological problems. In most places, it is classified as a prescription medicine, as it requires proper medical evaluation before use. This is because it may have interactions with other medications and is not suitable for all people, for example those with certain heart problems, hypotension, etc.

2. Health risks

Side effects: may cause side effects such as headache, dizziness, blurred vision, flushing (redness of the skin), nausea, and, in some cases, changes in blood pressure. Without prior medical evaluation, these side effects may not be properly managed and endanger the patient's health.

Drug interactions: Tadalafil may interact with medications such as nitrates (used for angina), and this interaction can cause a drastic drop in blood pressure, which can be life-threatening.

It is extremely important not to acquire or consume tadalafil without a valid medical prescription, as this not only violates the law in many places, but also seriously endangers the health of the individual. The prescription is an essential mechanism to ensure that a health professional has evaluated the patient's medical situation, including factors such as his medical history, possible allergies, and other medicines he is currently taking, to determine whether tadalafil is safe and suitable for him or her.