Head Injury While on Blood Thinners: When to Get Imaging

If you're on blood thinners and you hit your head-even if it feels like a minor bump-you can't afford to wait and see. The risk of internal bleeding in the brain is real, and it doesn't always show up right away. What feels like a simple fall or a bump on the head could turn into a life-threatening situation hours or even days later. That’s why imaging isn’t optional in these cases. It’s the first and most critical step.

Why Even a Small Head Injury Is Dangerous on Blood Thinners

People on anticoagulants like warfarin, rivaroxaban, apixaban, or aspirin have blood that doesn’t clot as easily. That’s good for preventing strokes or clots in the legs, but it’s dangerous when trauma happens. A small bleed inside the skull can grow slowly, with no obvious symptoms at first. By the time someone feels dizzy, confused, or vomits, it might already be too late.

Studies show that people on blood thinners are 2 to 3 times more likely to have a serious brain bleed after even a minor head injury than those not on these medications. The risk doesn’t disappear just because you didn’t lose consciousness or feel dizzy right away. In fact, many of the worst cases happen in people who seemed fine at first.

One study found that 0.5% to 1% of anticoagulated patients with a normal initial CT scan still developed a delayed bleed within days. That’s not rare. That’s one in every 100 to 200 people. And if you’re 65 or older, your risk goes up even more.

When Imaging Is Non-Negotiable

Guidelines from the American College of Emergency Physicians (ACEP) and state health departments like Washington State agree: if you’re on blood thinners and you’ve had a head injury, get a CT scan-right away.

You don’t need to wait for symptoms. You don’t need to be told you’re at risk. If any of these happened, get scanned:

• You lost consciousness-even for a few seconds
• You have confusion, trouble remembering things, or feel "foggy"
• You fell from a height (even just one level, like down stairs)
• You were hit directly on the head or neck
• You have a visible bump, cut, or bruise on your head
• You’re 65 or older
• You’re vomiting more than once
• You have trouble walking, speaking, or seeing clearly

These aren’t "maybe" signs. They’re triggers. Emergency rooms across the U.S. and Australia follow this protocol. If you’re on blood thinners and you’ve had any of these, you’ll be fast-tracked to the CT scanner. No waiting. No "let’s monitor you first."

What the CT Scan Looks For

The scan isn’t just a quick check. It’s a detailed look at the inside of your skull. The machine uses very thin slices-between 0.5 mm and 1.25 mm-to catch tiny cracks in the skull or small bleeds that might be missed with standard imaging.

Doctors are looking for:

• Subdural hematoma (blood between the brain and its outer lining)
• Epidural hematoma (blood between the skull and the brain’s outer covering)
• Intracerebral hemorrhage (bleeding inside the brain tissue)
• Skull fractures

Even a tiny amount of blood can be dangerous on blood thinners because it keeps spreading. A 2 mm bleed today could become a 20 mm bleed by tomorrow. That’s why timing matters.

What Happens After the Scan

If the CT scan shows no bleeding, you might still need to stay under observation. Some hospitals send you home after 6 hours if you’re stable, your INR is under 3.5 (if you’re on warfarin), and you have no other injuries. Others keep you overnight.

Why the difference? Because research shows delayed bleeds can happen up to 72 hours after the injury. One patient in a Texas hospital had a normal CT, stopped his rivaroxaban, and had a stroke three days later. That’s the catch: stopping your blood thinner can be just as dangerous as not treating the bleed.

So here’s the balance: you need to watch for new symptoms-worsening headache, confusion, weakness on one side, slurred speech, or seizures-while still staying on your medication unless a doctor tells you otherwise. Never stop your blood thinner on your own.

What You Shouldn’t Do

There are common mistakes people make after a head injury on blood thinners:

• Waiting to see if symptoms get worse
• Assuming a small bump means no problem
• Stopping your medication because you’re scared of bleeding
• Not telling the ER team you’re on blood thinners
• Ignoring dizziness or nausea because "it’s just a headache"

One of the biggest errors is assuming the Canadian CT Head Rule applies to you. That rule was made for healthy people with minor head injuries. It’s not meant for anyone on anticoagulants. Using it could miss up to 15% of serious bleeds.

What to Expect at the Emergency Room

When you arrive, they’ll check your vital signs and ask about your medication. They’ll want to know:

• What blood thinner you take (name and dose)
• When you last took it
• If you’ve had any recent falls or injuries
• Any history of brain bleeds or strokes

You’ll likely get a blood test-PT, INR, and type and screen-to check how well your blood clots. If your INR is too high (over 3.5 on warfarin), they may give you vitamin K or a clotting agent like PCC. If you’re on a DOAC like apixaban, they might use Idarucizumab (Praxbind) to reverse it quickly.

Then comes the CT scan. It’s fast-usually under 10 minutes. No needles, no pain. Just lie still while the machine takes pictures.

When to Go Back to the ER

If you’re sent home after a normal scan, you still need to watch for warning signs. Call 000 or go back to the ER immediately if you develop:

• A headache that gets worse instead of better
• Confusion, trouble recognizing people, or memory loss
• Weakness or numbness in your arm, leg, or face
• Slurred speech or trouble understanding others
• Seizures
• Vomiting more than twice
• Drowsiness or difficulty waking up

These aren’t "maybe" signs. They’re red flags. Even if it’s 2 a.m. or you think you’re overreacting-go. Delayed bleeds don’t wait for business hours.

What’s Changing in 2025

Doctors are starting to look beyond CT scans. Blood tests that detect brain proteins like UCH-L1 and GFAP (the Banyan Brain Trauma Indicator) are being studied to help decide who really needs a scan. Early results show promise, especially for older adults with mild symptoms.

Also, researchers are working on a modified version of the Canadian CT Head Rule specifically for people on DOACs. It’s expected to be ready in 2025. Until then, the safest rule is simple: if you’re on blood thinners and you hit your head, get scanned.

And if you’re over 65, living alone, or have a history of falls, talk to your doctor about fall prevention. The CDC’s STEADI program offers tools to reduce fall risk-like checking your vision, removing rugs, and reviewing medications that make you dizzy. Preventing the fall is just as important as treating the injury.

Frequently Asked Questions

What to Do Next

If you’re on blood thinners, keep a card or note in your wallet that lists your medication, dose, and doctor’s contact info. Wear a medical alert bracelet if you can. Talk to your doctor about fall prevention-especially if you’re older or have balance issues.

If you’ve recently had a head injury and haven’t been scanned yet, go to the ER now. Don’t wait. Don’t call your GP first. Go straight to the nearest emergency department. Tell them you’re on blood thinners. That one phrase changes everything.

Head injuries on blood thinners aren’t about being overly cautious. They’re about survival. The scan takes minutes. The risk of waiting? It’s not worth it.