Blood Thinner Overdose and Internal Bleeding: What to Do Immediately

If you're taking a blood thinner-whether it's warfarin, Eliquis, Xarelto, or Pradaxa-you know it's meant to keep you safe from clots. But what happens when you take too much? Or when a loved one accidentally takes a double dose? The truth is, blood thinner overdose doesn't always come with a warning. One minute you feel fine. The next, you're bleeding internally with no visible sign. And every hour counts.

What Happens When You Take Too Much?

Blood thinners work by slowing down your body’s ability to form clots. That’s good when you have atrial fibrillation or a history of DVT. But if your dose is too high, your blood can’t clot at all. Even a small bump can turn into a dangerous bleed inside your body. The most dangerous part? You might not feel it until it’s too late.

Warfarin, the oldest blood thinner, takes days to fully kick in. Your INR (a blood test that measures clotting time) might spike slowly-sometimes 12 to 24 hours after an overdose. But newer drugs like apixaban or rivaroxaban work fast. An accidental double dose can send your clotting time through the roof within hours. And unlike warfarin, there’s no easy way to check your levels at home with these.

Here’s what an overdose looks like in real life:

• Bloody or black, tarry stools
• Spitting up or coughing up blood
• Pink, red, or dark brown urine
• Vomiting material that looks like coffee grounds
• Unexplained bruising-especially large, spreading bruises
• Small red or purple dots under the skin (petechiae)
• Heavy menstrual bleeding that’s new or worse than usual
• Severe headache, dizziness, weakness, or confusion
• Sharp pain in your back, belly, or chest

These aren’t side effects. These are red flags. And they mean your body is bleeding inside-possibly into your brain, stomach, or kidneys.

When to Call 999 (Not Wait)

Too many people delay. They think, “It’s just a nosebleed.” Or, “I’ll wait until morning.” But when you’re on a blood thinner, waiting even a few hours can be deadly.

The NHS and Mayo Clinic both say: if bleeding from a cut, nose, or gum doesn’t stop after 10 minutes of direct pressure-call emergency services. Same if you see any of the symptoms above. Even if you feel fine.

A 2022 study by the National Blood Clot Alliance found that patients who got help within two hours of noticing bleeding had a 97% survival rate. Those who waited six hours or more? Only 76% made it.

One Reddit user, u/WarfarinWarrior, shared how he ignored dark stools for three days, thinking it was food. By the time he reached the ER, his hemoglobin had dropped to 6.2 g/dL (normal is 12-16). His INR was 8.7. He needed a blood transfusion and intensive care.

Don’t be that person. If you suspect an overdose-call now. Don’t text. Don’t ask a friend. Call 999.

What to Do Right Now

While you wait for help, here’s what you must do:

1. Do NOT take another dose. Even if you think you missed one. Overdose is not a missed dose-it’s too much.
2. Write down what you took. Name of the drug, how much, and when you took it. If you’re alone, leave a note on the counter. Emergency teams need this fast.
3. Don’t take ibuprofen, aspirin, or naproxen. These make bleeding worse. Even a single tablet can push you over the edge.
4. Lie down. Elevate any bleeding area above your heart if you can. This slows blood flow to the site.
5. Apply firm pressure. For external bleeding, press hard for at least 10 minutes. Don’t peek. Let the blood clot.

And here’s the one thing you should NOT do: try to “wait it out.” There’s no home remedy. No herbal tea. No vitamin K you can swallow to fix it. Not yet.

What Happens at the Hospital?

Emergency teams don’t guess. They test. They check your INR. They look for signs of bleeding in your brain, gut, or kidneys. Then they act.

If it’s warfarin and your INR is over 3.5, they’ll give you vitamin K-usually by mouth if you’re stable, or IV if you’re bleeding. But vitamin K takes hours to work. So if you’re actively bleeding, they’ll use something stronger: 4-factor Prothrombin Complex Concentrate (PCC). This is a concentrated mix of clotting factors that can reverse warfarin in minutes.

For newer drugs like Eliquis or Xarelto, there are specific antidotes:

• idarucizumab for Pradaxa (dabigatran)
• andexanet alfa for Eliquis and Xarelto (apixaban, rivaroxaban)

These cost thousands of pounds per dose-but they work fast. In under 15 minutes, they can restore your blood’s ability to clot. That’s why hospitals keep them on hand.

For very recent overdoses (within an hour), they might give you activated charcoal to stop the drug from absorbing. But after that? It’s too late. Your body already took it.

Who’s at Highest Risk?

It’s not just about how much you take. It’s about who you are.

People over 65 are four times more likely to have a serious bleeding event on blood thinners. Why? Slower metabolism. Kidney issues. More meds. The HAS-BLED score-a tool doctors use-gives you one point each for:

• Hypertension
• Abnormal kidney or liver function
• History of stroke
• Previous bleeding
• Unstable INR levels
• Age over 65
• Drinking alcohol or taking other drugs like NSAIDs

If your score is 3 or higher? You’re in the high-risk zone. That means you need more frequent checks. More education. And a clear plan for what to do if things go wrong.

How to Prevent This From Happening

Prevention beats emergency every time.

• Use a pill organizer. Not just any one-get one with alarms or one that locks. Many people accidentally take double doses because they forget if they already took it.
• Keep a bleeding risk checklist. Tape it to your fridge. List the symptoms above. Check it daily.
• Get regular INR tests. If you’re on warfarin, you need them weekly at first. Once stable, maybe monthly. Don’t skip them.
• Use a home INR monitor. These portable devices cost £200-£300. Studies show they cut major bleeding by 34%. If you’re high-risk, ask your doctor if you qualify.
• Tell every doctor you see. Dentists, pharmacists, surgeons-they all need to know you’re on a blood thinner. Even a simple tooth extraction can turn dangerous.
• Never mix with NSAIDs. Ibuprofen, naproxen, even aspirin for headaches? Avoid them. Use paracetamol instead.
• Keep a list of your meds. Include dosages and times. Carry it in your wallet. Your phone’s notes app doesn’t help if you’re unconscious.

What’s Changing in 2025?

There’s new hope. Ciraparantag-a universal reversal agent-is in final trials. It can reverse all blood thinners in under 10 minutes. No need to know which drug you took. No waiting for PCC or antidotes. Just inject and clotting starts.

The FDA approved it for emergency use in early 2025. Hospitals in the UK are starting to stock it. This could be the biggest advance since warfarin was invented in 1948.

But until then? You still need to know the signs. You still need to act fast.

Final Thought: This Isn’t Rare

In the UK, anticoagulant overdoses cause more emergency visits than insulin errors or opioid overdoses. The CDC says it’s the second most common serious medication error in people over 65.

You’re not alone. But you are responsible-for your own safety, and for the people who care about you.

If you take a blood thinner, you’re carrying a silent timer. You can’t see it. But it ticks every day. Don’t let it run out.

What Comes Next?

If you’ve made it this far, you’re thinking ahead. That’s good. But don’t stop here. Talk to your doctor. Ask about home INR monitors. Review your medication list. Talk to your family about the warning signs. Keep the checklist on your fridge.

This isn’t about fear. It’s about control. You’re not powerless. You just need to know what to look for-and when to act.