Some commonly used medicines can affect blood-clot risk in certain people. Learn which medications may be involved, warning signs of dangerous clots, and when to seek urgent medical care.
WARNING: Some Everyday Medicines May Affect Your Blood Clot Risk — Here’s How to Stay Safe
Many people take medicines every day without giving much thought to how those medications may affect the body. But certain medicines can influence blood clotting or, in specific circumstances, increase the risk of developing a blood clot.
That does not mean everyday medications are dangerous or that you should stop taking them. For most people, prescribed medicines are safe when used correctly. The important thing is understanding your individual risk factors and knowing which symptoms require medical attention.
What Is a Blood Clot?
A blood clot is a clump of blood that forms when blood changes from a liquid into a thicker, gel-like state.
Clotting is normally a protective process that prevents excessive bleeding after an injury. Problems can occur when a clot develops inside a blood vessel without an appropriate reason or travels to another part of the body.
A clot that develops in a deep vein, usually in the leg, is called deep vein thrombosis (DVT). If part of the clot travels to the lungs, it can cause a potentially life-threatening pulmonary embolism (PE).
Which Types of Medicines Can Influence Clot Risk?
The relationship between medication and blood clots depends heavily on the specific medicine, dose and a person’s health history.
1. Hormonal Medicines
Some medicines containing estrogen, including certain hormonal contraceptives and hormone therapies, can increase the risk of blood clots in some people.
The risk may be higher when other factors are present, such as smoking, obesity, prolonged immobility or a previous history of blood clots.
This does not mean everyone taking hormonal medication will develop a clot. A healthcare professional can help determine whether a particular medicine is appropriate for an individual.
2. Certain Cancer Treatments
Some cancer treatments and cancer itself can increase the likelihood of blood clots.
People undergoing cancer treatment may therefore require individualized monitoring, particularly when additional risk factors are present.
3. Medicines That Affect Bleeding
There is an important difference between blood clot risk and bleeding risk.
Medicines such as aspirin and anticoagulants are commonly used specifically to reduce the formation of harmful blood clots. However, they can increase bleeding risk.
For this reason, taking an aspirin or anticoagulant without medical advice is not a safe way to “prevent” blood clots.
Everyday Factors Can Matter Too
Medication is only one piece of the puzzle.
Your risk of developing a blood clot can also be affected by:
- Long periods of sitting or bed rest
- Recent surgery
- Pregnancy and the period after delivery
- Previous blood clots
- Certain inherited clotting conditions
- Some cancers
- Smoking
- Obesity
- Increasing age
- Certain chronic medical conditions
Having one risk factor does not automatically mean that a clot will develop. Risk generally depends on the combination of factors.
Warning Signs of a Blood Clot in the Leg
A DVT can sometimes occur without obvious symptoms. When symptoms do appear, they may include:
- Swelling in one leg
- Pain or tenderness, particularly in the calf
- Unexplained warmth in the affected area
- Redness or discoloration
- A feeling of heaviness or discomfort in the leg
These symptoms can have other causes, so they do not automatically mean someone has a blood clot. However, unexplained one-sided leg swelling or pain deserves medical evaluation.
Signs of a Blood Clot in the Lungs
A pulmonary embolism requires urgent medical attention.
Possible warning signs include:
- Sudden difficulty breathing
- Chest pain, especially pain that becomes worse with deep breathing
- Rapid heartbeat
- Coughing, sometimes with blood
- Feeling faint or suddenly very weak
If these symptoms occur suddenly or severely, seek emergency medical care immediately.
Do not wait to see whether the symptoms disappear.
Should You Stop Your Medication?
No—not simply because you are worried about blood clots.
Stopping a prescribed medication suddenly can sometimes create serious problems of its own. If you are concerned that a medicine may increase your clotting risk, speak with the doctor or pharmacist who prescribed it.
They can consider your medication, medical history and other risk factors and determine whether a change is necessary.
How Can You Reduce Your Risk?
There are several practical steps that may help reduce blood-clot risk, depending on your circumstances:
Stay physically active. Regular movement helps maintain healthy circulation.
Avoid sitting for very long periods. During long journeys, get up and move around when it is safe to do so.
Follow medical advice after surgery or illness. Some people may need specific clot-prevention measures during periods of limited mobility.
Know your personal risk factors. Tell your healthcare provider if you have previously experienced a blood clot or have a strong family history of clotting problems.
Take medicines exactly as directed. Never start or stop prescription medication solely because of something you read online.
The Bottom Line
The phrase “everyday pills can cause dangerous blood clots” is too broad. Medicines affect people differently, and only certain medications are associated with increased clotting risk under particular circumstances.
The safest approach is not to fear all medications, but to understand your specific medicine, know your personal risk factors and recognize the warning signs of a possible clot.
Sudden shortness of breath, chest pain, coughing blood or fainting can be signs of a medical emergency and should never be ignored.