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Health Education

What happens if you miss a dose of blood thinner?

Step 1: Reach out to your healthcare provider for advice. Then, read these recommendations.
Sarah Bradley writer headshot
By | Feb. 24, 2025 Medically reviewed by J. Elizabeth Allen, DO, FACEP
Alarm clock next to a bottle of pills - What happens if you miss a dose of blood thinner?

Key takeaways

  • Blood thinners help prevent blood clots in people with certain health conditions, like atrial fibrillation, deep vein thrombosis, and a history of stroke or heart attack.

  • If you’re taking blood thinners, you’re at risk of a potentially life-threatening blood clot, so it’s critical to follow the prescribed dosing schedule for this medication.

  • If you miss a dose of blood thinners, it’s best to ask your healthcare provider about what to do next.

  • Generally speaking, when you miss a dose of a medication, you should take it as soon as you remember, or—if it’s close to your next dose—skip the missed dose and resume taking your medication at the usual time.

  • Never take two doses of blood thinners at the same time. This increases your risk of bleeding, as well as other complications.

In this article:

Blood thinners are prescription drugs that keep your blood from thickening or clumping, preventing potentially life-threatening blood clots. They include anticoagulant and antiplatelet medications like heparins, Coumadin (warfarin), and aspirin, as well as newer-generation anticoagulants like Eliquis (apixaban) and Xarelto (rivaroxaban). Although they don’t actually make your blood thinner, these medications reduce your body’s normal blood clotting response to prevent existing blood clots from growing and new ones from forming.

Blood thinners are often prescribed to people with conditions that put them at a higher risk for forming blood clots, says Sarah Bonza, MD, primary care and family medicine physician. These include medical conditions such as atrial fibrillation (AFIB), deep vein thrombosis (DVT), coronary artery disease, a history of stroke, and clotting disorders. But different types of blood thinners have different half-lives, Dr. Bonza adds, and it’s important to follow a strict dosing schedule because missing a dose can lower your medication’s effectiveness while increasing your risk for blood clots and complications like stroke.

What happens if you miss a dose?

All medications work more safely and effectively when you take them according to the prescribed dosing schedule, but nearly everyone misses a dose of medication from time to time. For some medications, missing a dose is a minor problem: You take it as soon as you remember or hold off until your next dose and then get back on track with little to no side effects.

Blood thinners, however, need to be taken as consistently as possible. Missing even a single dose could lead to a stroke or blood clot, says Brian Bostick, MD, a cardiologist with the University of Missouri Health Care, especially if you are managing a serious health condition or at high risk of clotting.

That said, there are varying degrees of seriousness when it comes to missing a single dose of blood thinner, and the effects may not be immediately obvious, says Allison Hinkle, Pharm.D., CPH, clinical pharmacy manager with HCA Florida Healthcare. A missed dose of one type of medication can be more dangerous compared to others, depending on the specific medication and your reason for taking it.

People taking warfarin, for example, have to undergo regular blood tests to monitor their international normalized ratio (INR), a measurement of how long it takes your blood to clot: “Missing one dose can affect your INR for days or weeks, leading to under- or over-anticoagulation,” Dr. Hinkle explains. “Missing one or several doses of anticoagulants can cause blood clots that reduce or eliminate blood flow to extremities or vital organs, or even result in a stroke or pulmonary embolism.”

There is less room for error in dosing when taking warfarin because it’s processed out of your body more quickly, in just 20 to 60 hours, says Dr. Bonza. Newer generation blood thinners like Xarelto and Eliquis leave your system even more quickly: Xarelto in five to nine hours, and Eliquis in about 12 hours.

Heparin is also short-acting, she says, but aspirin—which is often given to people with a history of heart attack or coronary heart disease—lasts in the body for seven to 10 days. It may be less serious to miss a single dose of aspirin compared to warfarin or heparin, but you should always try to stick to your prescribed dosing schedule no matter which drug you’re taking.

How to manage a missed dose

If you’ve missed a dose of blood thinner, you may be wondering: Should you take it as soon as you remember or wait until your next dose?

Unless you’ve already been given instructions on how to handle this scenario, Dr. Hinkle recommends contacting your healthcare provider or pharmacist as soon as you realize you missed a dose: “Since the half-life is different for each blood thinner, and the amount of blood thinner required in the bloodstream to achieve a therapeutic effect can be vastly different for each person, you need to take an individualized approach [to correcting your missed dose].”

For example, she explains that someone taking warfarin for thrombosis prevention because of atrial fibrillation is managed differently than someone taking it for thrombosis prevention due to an artificial heart valve. Your provider could tell you to take the missed dose as soon as you remember or wait until your next dose is due to catch up.

In general, Dr. Bonza says the recommendation for a missed dose varies based on how often you normally take your blood thinner and how much time you have left until your next dose.

If you take a once-daily blood thinner, like over-the-counter aspirin:

  • Take it as soon as you can unless it’s almost time for your next dose. Then, skip the missed dose and resume your usual schedule.

If you take a twice-daily blood thinner, like Eliquis:

  • If it’s within six to eight hours of your usual dosing schedule, take it as soon as you remember. If it’s more than that (i.e., your next dose is coming up soon), skip the missed dose and take the next dose at the usual time, even if that’s the next day.

If you’ve missed several doses of your medication, you may need to be evaluated by a healthcare professional for blood clots or have your dose adjusted temporarily, says Dr. Hinkle. Regardless of how often you usually take your blood thinner or how many doses you have missed, never take a double dose of your medication or take two doses close together.

What happens if you take a double dose of blood thinners

Your body needs the right amount of blood-thinning medication to prevent blood clots without causing other possible side effects, like excessive bleeding. Dr. Bonza says it’s critical to be mindful of the timing of your next dose when making up for a missed dose: doubling up on your blood thinner can be dangerous and even fatal, increasing your risk of severe bleeding.

According to Dr. Hinkle, taking additional doses of blood thinner can also result in organ damage to your liver or kidneys, unusual bruising, brain bleeding (hemorrhagic stroke), nausea, and vomiting. Bleeding because of a blood thinner overdose can look like many different things, including increased menstrual bleeding; blood in your urine (brown urine); nosebleeds; coughing up blood; bloody, black, or tarry stools; or vomiting material that resembles coffee grounds.

The bottom line

If you miss a dose of blood thinners, the best thing to do is contact your healthcare provider for guidance. Because different medications stay in your system for different lengths of time, your provider may recommend you take the missed dose as soon as possible or wait until your next dose. The reason why you’re taking blood thinners is important, too, with some health conditions requiring more immediate intervention for a missed dose than others.

In general, experts recommend that you take your missed dose of blood thinner as soon as you remember unless it’s very close to your next dose; in that case, skip the missed dose and take your next one at the usual time. If you develop any new symptoms after missing a dose of blood thinner, Dr. Bostick says it’s important to contact your healthcare provider and let them know.