Taking one extra losartan tablet is unlikely to cause serious harm for most people, but it can drop your blood pressure lower than normal. The main risk is hypotension, meaning your blood pressure falls below 90/60 mmHg, which can cause dizziness, lightheadedness, or fainting. How your body handles that extra dose depends on factors like your prescribed dose, your kidney function, and what other medications you take.
What an Extra Dose Does to Your Body
Losartan works by relaxing blood vessels, which lowers blood pressure. When you take more than your prescribed amount, that effect gets amplified. Your blood vessels relax more than intended, and your blood pressure can dip to a level your body struggles to compensate for.
The most common symptoms of taking too much losartan are dizziness, feeling faint (especially when standing up), and a fast or slow heartbeat. These symptoms tend to appear within a few hours, since losartan itself has a half-life of about 2 hours, though its active breakdown product stays in your system for 6 to 9 hours. That means the effects of an extra dose can linger for the better part of a day.
If your body’s normal compensatory mechanisms can keep up, you may feel slightly lightheaded or notice nothing at all. If they can’t, you could experience more noticeable drops in blood pressure that lead to confusion, weakness, or passing out.
When One Extra Pill Becomes Riskier
A single accidental double dose is a very different situation from swallowing handfuls of tablets. For most healthy adults on a standard dose, doubling up once will cause mild symptoms at worst. But certain factors raise the stakes considerably.
- Dehydration: If you haven’t been drinking enough fluids, are sick with vomiting or diarrhea, or have been sweating heavily, your blood volume is already lower than usual. An extra dose on top of that can push your blood pressure down faster and further.
- Diuretics or other blood pressure medications: If you take a water pill or another blood pressure drug alongside losartan, doubling the losartan compounds the blood-pressure-lowering effect of your entire regimen. This combination significantly increases the risk of symptomatic low blood pressure.
- Kidney problems: Losartan affects how your kidneys handle potassium. An extra dose can raise potassium levels in your blood, and this effect is more pronounced in people who already have reduced kidney function or diabetes with kidney involvement. Elevated potassium is concerning because it can affect your heart rhythm.
- Older age: Blood pressure regulation slows with age. Older adults are more likely to experience dizziness or falls from a blood pressure drop.
What to Watch For
After taking an extra dose, pay attention to how you feel over the next several hours. Mild dizziness or lightheadedness when you stand up is the most common effect and usually passes on its own. Sit or lie down if you feel unsteady, and drink water to support your blood volume.
More serious warning signs include fainting, a heartbeat that feels very fast or unusually slow, confusion, difficulty speaking, blurred vision, or severe nausea. These suggest your blood pressure has dropped to a level your body can’t easily correct. Persistent blood pressure below 90/60 mmHg can reduce blood flow to your brain and organs, so these symptoms warrant immediate attention.
What to Do Right Now
If you just took one extra tablet and feel fine, the situation is probably manageable at home. Stay hydrated, avoid alcohol, and skip any strenuous activity for the rest of the day. Don’t stand up quickly from sitting or lying positions, since that’s when low blood pressure is most likely to cause dizziness or a fall. Skip your next dose if it’s coming up soon, and return to your normal schedule after that. Do not take a double dose to “make up” for a missed one in the future.
If you’re experiencing symptoms or you’re unsure whether your situation is serious, Poison Control offers free, confidential guidance 24 hours a day at 1-800-222-1222 or through their online tool at webPOISONCONTROL. They can help you assess whether you need medical evaluation based on your specific dose, other medications, and symptoms.
Call 911 if you faint, have a seizure, have trouble breathing, or can’t stay awake. There is no antidote for losartan, and it can’t be removed through dialysis because of how tightly it binds to proteins in your blood. Treatment for a serious overdose is supportive: IV fluids to raise blood pressure and close monitoring until the drug clears your system.
The Potassium Factor
One effect people don’t always think about is potassium. Losartan blocks a hormonal pathway that normally helps your kidneys excrete potassium. Taking more losartan than prescribed means more potassium stays in your bloodstream. For a one-time extra pill in someone with healthy kidneys, this is rarely a problem. But if you already have kidney disease, take potassium supplements, or use a potassium-sparing diuretic, even a single extra dose could nudge your potassium into a range that affects your heart. Symptoms of high potassium include muscle weakness, tingling or numbness, and an irregular heartbeat.
How Long the Effects Last
Losartan’s active metabolite, which does most of the blood-pressure-lowering work, has a half-life of 6 to 9 hours. This means it takes roughly 24 to 36 hours for the extra dose to fully clear your system. Most people feel back to normal well before that, typically within 12 hours, as their blood pressure gradually returns to its usual range. If you’re still feeling off after a full day, that’s worth a call to your doctor or pharmacist to make sure nothing else is going on.