What Happens If I Don't Take Blood Thinners After Surgery? Risks and Consequences

October 14, 2025 •

4 min read

Half of all blood clots occur during or within 90 days of a surgery or hospital stay [1.7.2]. This statistic underscores a critical question for many patients: What happens if I don't take blood thinners after surgery?

Quick Summary

Not taking prescribed anticoagulants after surgery elevates the risk of forming dangerous blood clots, which can lead to deep vein thrombosis (DVT), pulmonary embolism (PE), heart attack, or stroke [1.2.5].

Key Points

Increased Clot Risk: Not taking blood thinners after surgery dramatically increases your risk of deep vein thrombosis (DVT) and pulmonary embolism (PE) [1.2.1, 1.2.5].
DVT Symptoms: Be aware of DVT symptoms like leg pain, swelling, warmth, and redness [1.9.1].
PE is a Medical Emergency: A PE can be fatal; symptoms include sudden shortness of breath, chest pain, and dizziness [1.9.4].
High-Risk Surgeries: The risk is especially high after major orthopedic (hip/knee), abdominal, pelvic, and cancer surgeries [1.5.3, 1.6.1].
Medication is Prescribed for a Reason: Your surgeon has determined that the benefit of preventing a deadly clot outweighs the medication's bleeding risks [1.3.4].
Complete the Full Course: Treatment duration can range from 10 days to over a month; it is critical to finish the entire prescription [1.8.5].
Never Stop on Your Own: Do not stop taking your blood thinner without consulting your healthcare provider, as this can lead to a sudden increase in clot risk [1.2.5].

Why Are Blood Thinners Prescribed After Surgery?

After a surgical procedure, the body's natural clotting process is activated. However, periods of prolonged immobility during recovery can cause blood flow to slow down, particularly in the legs [1.5.3]. This environment makes it easier for blood to pool and form clots [1.2.2]. Anticoagulants, commonly known as blood thinners, are medications that interrupt this clotting process, significantly lowering the risk of developing a dangerous clot [1.6.1].

Certain operations carry a higher risk, including major surgeries on the abdomen, pelvis, hips, or legs [1.5.3]. Orthopedic procedures like knee or hip replacements are particularly high-risk [1.5.4, 1.6.1]. For these patients, adhering to a blood thinner regimen is a crucial part of a safe recovery [1.2.2].

The Primary Dangers: DVT and Pulmonary Embolism

Skipping your prescribed anticoagulant medication directly increases your risk for serious thromboembolic events [1.2.5]. The two most critical conditions to be aware of are Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE).

Deep Vein Thrombosis (DVT)

A DVT is a blood clot that forms in one of the deep veins of the body, usually in the legs [1.5.3]. The incidence of DVT after surgery can range from as low as 2.2% to as high as 60% in orthopedic patients who do not receive preventative treatment [1.4.1, 1.4.2]. Symptoms are not always obvious, but can include:

Pain or tenderness in the leg, not necessarily near the incision site [1.9.1, 1.9.5].
Swelling in the affected leg [1.9.2, 1.9.5].
Warmth and redness or discoloration of the skin [1.9.1, 1.9.5].

Pulmonary Embolism (PE)

The most life-threatening risk of a DVT is that a piece of the clot can break off, travel through the bloodstream, and become lodged in the lungs. This blockage is called a pulmonary embolism (PE) and can be fatal [1.2.2, 1.5.3]. PE is the third most common cause of cardiovascular death worldwide [1.5.2]. The risk of developing a PE is highest in the first one to six weeks after surgery [1.5.2].

Symptoms of a PE are a medical emergency and include:

Sudden shortness of breath [1.9.4, 1.9.5].
Sharp chest pain, which may worsen with breathing [1.9.4, 1.9.5].
A feeling of anxiety, dizziness, or lightheadedness [1.9.4].
Rapid or irregular heartbeat [1.9.4].
Coughing, sometimes with blood [1.9.4].

Adherence vs. Non-Adherence: A Comparison

Deciding to skip medication has direct consequences, while taking it as prescribed offers significant protection. The choice is a balance between preventing life-threatening clots and managing the primary side effect of anticoagulants, which is an increased risk of bleeding [1.3.3]. Your surgeon has determined that the benefit of preventing a clot outweighs the bleeding risk for your specific situation.


Aspect	Benefit of Taking Blood Thinners	Risk of Not Taking Blood Thinners
Clot Prevention	Significantly lowers the risk of DVT and PE [1.5.4]. Prophylaxis can reduce TE events by up to 90% [1.5.4].	High risk of developing DVT, especially after orthopedic, cancer, or major abdominal surgery [1.6.1, 1.5.3].
Major Health Events	Prevents potentially fatal PE, stroke, or heart attack [1.2.5].	A DVT can travel to the lungs, causing a life-threatening PE [1.2.2].
Recovery	Allows for a safer recovery period when mobility is limited [1.2.2].	Can lead to emergency hospitalization, long-term complications like post-thrombotic syndrome (chronic leg pain/swelling), and even death [1.9.3, 1.5.3].
Side Effects	Managed risk of bleeding, which your doctor monitors [1.2.3].	Complications from a major clot are far more severe than the managed risks of the medication [1.3.4].

Types of Post-Surgical Blood Thinners & Duration

Your surgeon will prescribe a specific type and dosage of blood thinner based on your surgery, medical history, and risk factors [1.6.1]. Common options include:

Injectables: Low-molecular-weight heparin (LMWH) like enoxaparin is frequently used, especially after major general, orthopedic, or gynecologic surgeries [1.6.1].
Oral Anticoagulants: These include warfarin and newer direct oral anticoagulants (DOACs) like apixaban (Eliquis) and rivaroxaban (Xarelto) [1.2.2]. Aspirin may also be used in some cases, particularly after orthopedic trauma surgery [1.7.3].

The duration of treatment varies. After a knee replacement, you might take a blood thinner for 10 to 14 days, while after a hip replacement, it could be for 32 to 38 days [1.8.5]. For some major surgeries, treatment can extend up to 35 days or longer [1.8.2]. It is vital to complete the full course as prescribed.

Conclusion: A Non-Negotiable Component of Recovery

Ultimately, the answer to 'What happens if I don't take blood thinners after surgery?' is that you are taking a significant and unnecessary gamble with your health. The risk of developing a deep vein thrombosis or a fatal pulmonary embolism is real and substantially increased by non-adherence [1.2.5, 1.3.1]. While all medications have potential side effects, your medical team has prescribed anticoagulants because the protective benefits far outweigh the manageable risks [1.3.4]. Always communicate with your healthcare provider about any concerns or side effects, but never stop taking your medication without their direct instruction [1.2.5].

For more information on blood clot prevention, you can visit the National Blood Clot Alliance: https://www.stoptheclot.org/ [1.2.3]

Frequently Asked Questions

The main reason is to prevent the formation of dangerous blood clots, such as deep vein thrombosis (DVT), which can form due to immobility during recovery. These clots can travel to the lungs and cause a life-threatening pulmonary embolism (PE) [1.2.1, 1.2.2].

The duration depends on the type of surgery. For a knee replacement, it's often 10-14 days, while a hip replacement may require 32-38 days. For some major procedures, it can be up to 35 days or more [1.8.2, 1.8.5].

For a DVT in the leg, initial signs include pain or tenderness, swelling, warmth, and skin redness [1.9.1]. For a PE in the lungs, symptoms are sudden shortness of breath and chest pain [1.9.4].

No, you should not substitute medication without your doctor's approval. While aspirin is sometimes used, especially after orthopedic trauma, your surgeon prescribed a specific anticoagulant based on your risk profile. Only change your medication under medical guidance [1.7.3, 1.2.2].

Missing a single dose can increase your risk of a blood clot by allowing the anticoagulant level in your blood to drop. If you remember within a few hours, take it. If it's close to your next scheduled dose, skip the missed one and continue your normal schedule. Do not double up. Contact your provider for specific advice [1.2.5].

Mechanical methods like compression stockings or intermittent pneumatic compression devices can be used, sometimes in conjunction with medication. Early and frequent movement or ambulation is also crucial. However, for high-risk surgeries, these are often not sufficient on their own and are not a substitute for prescribed anticoagulants [1.6.1, 1.6.6].

Major orthopedic surgeries like hip and knee replacements have a very high risk. Other high-risk procedures include major surgery for cancer, major abdominal or pelvic surgery, and neurosurgery [1.5.3, 1.5.4, 1.6.1].