Do blood thinners make you feel any different? Understanding the Side Effects

October 8, 2025 •

4 min read

As of 2020, over 7.6 million adults in the U.S. use oral anticoagulants [1.5.1]. If you're one of them, you may wonder, do blood thinners make you feel any different? While many people don't feel a change, some experience noticeable effects.

Quick Summary

Blood thinners can cause side effects like fatigue, dizziness, nausea, and easier bruising. While often mild, these symptoms can sometimes signal more serious issues like internal bleeding.

Key Points

No Change is Common: Many people do not feel any different while taking blood thinners; the medication works without causing noticeable sensations.
Potential for Fatigue and Dizziness: Some users may experience fatigue, weakness, or dizziness, which can sometimes be linked to a lower blood count [1.2.2, 1.9.1].
Bruising is a Key Sign: One of the most common physical changes is bruising more easily from minor bumps [1.10.1].
Bleeding is the Main Risk: The most serious side effect is excessive bleeding. Signs include blood in urine/stool, prolonged nosebleeds, or coughing up blood [1.11.4].
Two Main Types: Blood thinners are mainly anticoagulants (like warfarin, Eliquis) which block clotting proteins, or antiplatelets (like aspirin) which stop platelets from clumping [1.6.1].
Interactions Matter: Other medications, certain foods (especially with warfarin), and alcohol can alter the effects of blood thinners and change how you feel [1.2.1, 1.7.1].
Communication is Crucial: Always tell your doctor about any side effects or different feelings you experience while on the medication [1.7.1].

The Purpose and Types of Blood Thinners

Blood thinners are essential medications prescribed to prevent blood clots that can lead to serious conditions like heart attacks and strokes [1.4.2]. It's a common misconception that these drugs actually 'thin' the blood. Instead, they work by interfering with the clotting process [1.9.3]. There are two main categories of blood thinners [1.6.1]:

Anticoagulants: These drugs, such as warfarin (Coumadin), apixaban (Eliquis), and rivaroxaban (Xarelto), work by slowing down the body's process of making clots. They interfere with clotting factor proteins in the blood [1.6.2, 1.6.1]. They are often used to treat or prevent conditions like deep vein thrombosis (DVT) and pulmonary embolism (PE) [1.6.1].
Antiplatelets: This group, which includes aspirin and clopidogrel (Plavix), prevents blood cells called platelets from clumping together to form a clot [1.6.1]. They are frequently prescribed for individuals who have a history of heart attack or stroke [1.6.1].

So, Do Blood Thinners Make You Feel Any Different?

For many patients, the answer is no—they don't feel any different on a day-to-day basis. The medication works silently in the background. However, some people do experience side effects that can make them feel different. These feelings can range from mild and manageable to severe and requiring immediate medical attention.

Common Sensations and Side Effects

Some of the more common, non-bleeding side effects can affect your daily sense of well-being. A low blood cell count, which can be an adverse effect of blood thinners, may cause you to feel sick [1.2.1, 1.2.2].

Common feelings and side effects include:

Fatigue, Weakness, or Dizziness: Feeling more tired or weaker than usual can be a side effect. This may be linked to the medication itself or potentially a low blood count (anemia) resulting from slow, unnoticed bleeding [1.2.1, 1.9.4].
Nausea or Upset Stomach: Some individuals report feeling nauseous, especially when first starting the medication. Indigestion and diarrhea or constipation can also occur [1.2.3, 1.8.4].
Easier Bruising: One of the most common signs of being on a blood thinner is bruising more easily [1.10.1]. Minor bumps can result in noticeable bruises because the medication makes blood vessels more fragile and slows clotting [1.3.3].
Headaches: Headaches can be a possible side effect for some people taking anticoagulants [1.2.3]. While often benign, a new or unusually severe headache should be reported to a doctor, as it could be a sign of a more serious issue [1.3.1].

Comparison of Blood Thinner Types

While all blood thinners increase bleeding risk, their specific mechanisms and other side effects can differ.


Feature	Anticoagulants (e.g., Warfarin, Eliquis)	Antiplatelets (e.g., Aspirin, Plavix)
Primary Mechanism	Interfere with clotting factor proteins in the coagulation cascade [1.6.5].	Prevent platelets from sticking together to form a clot [1.4.2].
Common Uses	Atrial fibrillation (AFib), deep vein thrombosis (DVT), pulmonary embolism (PE) [1.6.1].	Prevention of heart attack and stroke, especially after a prior event or stent placement [1.4.3, 1.6.1].
Common Side Effects	Nausea, fatigue, hair loss (less common), easy bruising [1.2.2, 1.3.4, 1.3.3].	Upset stomach, indigestion, diarrhea, skin rash, itching [1.4.1, 1.4.5].
Monitoring	Warfarin requires regular blood tests (INR) to monitor effectiveness. Newer DOACs (like Eliquis, Xarelto) typically do not [1.7.1].	Generally do not require routine blood monitoring [1.7.1].

Serious Side Effects: When to Seek Medical Help

The most significant risk associated with all blood thinners is excessive bleeding [1.11.4]. This can be external or internal. It is crucial to be aware of the signs of serious bleeding and to contact your doctor or seek emergency care if they occur [1.8.3].

Seek immediate medical attention for these signs [1.8.4, 1.3.5]:

Bleeding from a cut that won't stop after 10-15 minutes of pressure [1.2.1].
Prolonged or frequent nosebleeds (lasting longer than 10 minutes) [1.2.3].
Blood in the urine (red or brown) or stool (bright red or black and tarry) [1.2.4].
Coughing up or vomiting blood, which may look like coffee grounds [1.2.4].
A severe, unusual headache or sudden vision changes [1.3.1, 1.2.4].
Sudden weakness or numbness, especially on one side of the body [1.8.3].
A serious fall or a significant blow to the head [1.8.4].
Sudden chest pain or difficulty breathing [1.2.3].

Lifestyle and Medication Interactions

How you feel on blood thinners can also be influenced by your diet, other medications, and lifestyle choices.

Medication Interactions: Many other drugs, including over-the-counter NSAIDs (like ibuprofen and naproxen), certain antibiotics, and even herbal supplements (like ginkgo biloba and St. John's wort), can interact with blood thinners and increase bleeding risk [1.2.1].
Dietary Considerations: If you take warfarin, it's important to maintain a consistent intake of vitamin K, which is found in leafy green vegetables like spinach and kale, as it can interfere with the medication's effectiveness [1.7.1, 1.7.3]. For most newer anticoagulants, these dietary restrictions don't apply [1.7.4].
Alcohol: Excessive alcohol consumption can affect how your body processes the medication and can increase your risk of bleeding, partly by increasing the risk of falls [1.2.2, 1.7.1].

Conclusion

So, do blood thinners make you feel any different? The experience varies. While many people tolerate them with no noticeable changes, others may feel fatigued, dizzy, or nauseous. The most common physical sign is easier bruising. It's crucial to distinguish between these manageable side effects and the signs of serious bleeding. Always maintain open communication with your healthcare provider about how you are feeling, report any new or worsening symptoms, and never stop taking your medication without their guidance [1.8.2]. Being informed and vigilant allows you to manage your health effectively while on these life-saving drugs.

For more detailed information on anticoagulants, you can visit resources like the National Blood Clot Alliance.

Frequently Asked Questions

Yes, feeling tired, weak, or fatigued can be a side effect of blood thinners. This might be due to a lower blood count (anemia), which can result from slow, unrecognized bleeding [1.9.1, 1.9.4].

Blood thinners reduce your blood's ability to clot, and they can make small blood vessels more fragile. This means even a minor bump can cause bleeding under the skin, resulting in a bruise [1.3.3, 1.10.1].

The most serious side effect is major bleeding. You should seek immediate medical help for symptoms like red or black stool, urine that is red or brown, severe headaches, coughing up blood, or any bleeding that doesn't stop [1.8.4].

If you are taking warfarin, you need to be consistent with your intake of vitamin K, found in leafy greens [1.7.1]. For newer anticoagulants like Eliquis and Xarelto, there are generally no major dietary restrictions [1.7.4].

It is generally advised to limit alcohol intake. Heavy drinking can affect how the medication is metabolized and increases your risk of falls and subsequent bleeding [1.2.2, 1.7.1].

Anticoagulants (e.g., warfarin, Eliquis) slow down the chemical reactions that create clotting proteins. Antiplatelets (e.g., aspirin) prevent platelet cells from sticking together to form a clot [1.6.1, 1.6.2].

Some people may experience side effects like nausea, dizziness, or an upset stomach when starting blood thinners, but many do not [1.2.2, 1.4.5]. If these symptoms persist, you should talk to your doctor.