Taking blood pressure tablets without a doctor’s advice can lower your blood pressure too much and cause dizziness, weakness, fainting, or a slow heartbeat; some medicines can also cause swelling, fatigue, or a cough depending on the drug. Blood pressure medicines are not all the same, and side effects vary by type, so taking the wrong one or the wrong dose can be risky.

What can happen

  • Low blood pressure: You may feel lightheaded, shaky, or faint if your pressure drops too far.
  • Dizziness and fatigue: These are common when the body is adjusting to blood pressure medicines.
  • Headache or weakness: These can happen if blood pressure falls below your normal range.
  • Swelling or cough: Some medicines, such as calcium channel blockers or ACE inhibitors, can cause these effects.
  • Danger if you already take BP medicine: Changing or stopping treatment suddenly can let blood pressure rebound to a dangerous level.

When it is urgent

Get emergency help now if the person has chest pain, trouble breathing, passes out, has confusion, or cannot stay awake. Very low blood pressure or a severe reaction can become dangerous quickly.

What to do

If someone took BP tablets by mistake, do not take another dose until a clinician or pharmacist advises you. If they feel dizzy, have them sit or lie down, and if symptoms are severe or worsening, seek urgent medical care right away.

TL;DR: BP tablets without medical advice can make blood pressure fall too low or cause other side effects, and the risk depends on the specific medicine and dose.