Cannabis and Blood Thinners

by | Jun 4, 2024 | Massachusetts, Medical Marijuana

In states that have legalized cannabis products for recreational use, many people wonder if they should keep their medical marijuana cards. A medical card means visiting a physician annually (or twice a year in some states), an added expense.

Today, most states have legalized cannabis use for medical purposes. This is good news for patients suffering from symptoms that can be improved by cannabis. However, it also raises questions about the safety of pairing medical marijuana with other medications.

So, cannabis and blood thinners: how do they react? Does Warfarin and marijuana smoking increase blood clotting risks? Let’s find out.

Health Risks Associated With Blood Clotting

Do you know how the plumbing in your house can become clogged and obstruct the water flow? Human arteries are not much different. Over time, plaque and other deposits can narrow within the arteries, causing increased blood pressure, circulatory problems, and increased risk of problems with blood clotting.

Blood clots can cause various serious health problems depending on their location in the body. Individuals who are over the age of forty with one or more of the following health conditions have the highest risk of developing problems with blood clotting:

  • Obesity
  • Lung Problems
  • Anemia
  • Arthritis
  • Cancer
  • Diabetes
  • Pregnancy
  • Chronic Inflammation
  • Hypertension (High-Blood Pressure)

Some studies share that a sedentary lifestyle (low physical activity) has become a significant contributor to the development of potentially life-threatening blood clots. Make time to be physically active for thirty minutes to one hour daily (with a safe elevated heart rate); it may substantially reduce your risk factors.

Deep Vein Thrombosis (DVT)

One common issue is deep vein thrombosis (DVT), where a clot forms in the deep veins, usually in the legs, leading to swelling, pain, redness, and warmth in the affected area. If a DVT clot dislodges, it can travel to the lungs and cause a pulmonary embolism (PE), characterized by shortness of breath, chest pain, rapid heart rate, and sometimes coughing up blood. PE is a life-threatening condition requiring immediate medical attention.

Myocardial Infarction

Another primary concern is a heart attack, or myocardial infarction, which occurs when a clot blocks one of the coronary arteries that supply blood to the heart muscle. Symptoms include chest pain or discomfort, pain in other areas such as the arms or jaw, shortness of breath, sweating, nausea, and lightheadedness. Prompt treatment is essential to prevent significant heart muscle damage or death.

Ischemic Stroke

Ischemic stroke is another severe condition caused by blood clots, where a clot blocks blood flow to the brain, leading to sudden numbness or weakness, confusion, trouble speaking, vision problems, and loss of coordination. This can result in permanent brain damage, disability, or death.

A transient ischemic attack (TIA), often called a “mini-stroke,” is a “temporary blockage with similar symptoms that resolve quickly but indicate a higher risk of a future and potentially life-threatening stroke.

Peripheral Artery Disease (PAD)

Peripheral artery disease (PAD) involves clots in the arteries supplying blood to the limbs, typically the legs, causing leg pain when walking, numbness, coldness, sores, and changes in leg color. Severe PAD can lead to limb ischemia, gangrene, and possibly amputation if untreated. Additionally, Budd-Chiari syndrome is a rare condition where clots block the hepatic veins, leading to abdominal pain, fluid buildup, liver enlargement, and jaundice, potentially resulting in liver failure.

Early recognition and treatment of blood clots are crucial to preventing severe complications and improving outcomes. If you experience any symptoms suggestive of a blood clot, it is essential to seek medical attention immediately.

A Brief Introduction to Blood Thinners

Blood clots are the body’s way of preventing blood from flowing. In some cases, blood clots form inside the bloodstream, which can be dangerous and life-threatening. Without the body’s blood clotting mechanisms, an external flesh wound will continue to bleed, but blood clots pose substantial risks if they travel through a vein or artery.

Blood thinners, also known as anticoagulants and antiplatelet drugs, are medications that help prevent blood clots from forming or growing larger. They are essential for individuals with conditions like atrial fibrillation, deep vein thrombosis, or those who have had heart attacks or strokes. By reducing the blood’s time to clot, blood thinners lower the risk of potentially life-threatening events such as strokes and heart attacks.

Two Different Types of Blood Thinner Medications

There are two main types of blood thinners: anticoagulants and antiplatelet agents. Anticoagulants, like Warfarin and newer medications like apixaban and rivaroxaban, work by interfering with the body’s body’s process. They are often prescribed for long-term use in managing chronic conditions.

Antiplatelet drugs, such as Aspirin, prevent platelets (a type of blood cell) from clumping together to form clots. They are commonly used to protect people who have had heart attacks or certain kinds of strokes.

While blood thinners are incredibly beneficial, they require careful monitoring. They can increase the risk of bleeding, so following your healthcare provider’s instructions closely and attending regular check-ups is essential. Additionally, certain foods and other medications can affect how blood thinners work, so always keep your healthcare team informed about any changes in your diet or new medications.

Blood thinners play a crucial role in managing and preventing severe cardiovascular conditions, helping many people live healthier, safer lives.

What Blood Thinner Medications Are Prescribed and How Do They Work?

Some prescription and over-the-counter medications (Aspirin) can effectively lower the risk of developing blood clots. Heart attacks and strokes are caused by blood clots that cannot be reabsorbed into the bloodstream. When those blood clots travel, dangerous health problems can occur.

Blood thinners are a group of medications that help prevent the development of blood clots or reduce the size of new blood clots. Here are the common blood thinners prescribed to patients and how they work.


Warfarin is a commonly prescribed anticoagulant, or blood thinner, used to prevent blood clots in people at risk of developing them. It is often recommended for individuals with conditions such as atrial fibrillation, deep vein thrombosis or those who have had a heart attack or stroke.

How Warfarin Works

Warfarin works by inhibiting the action of vitamin K, essential for producing certain clotting factors in the liver. These clotting factors are proteins needed for blood to clot properly. By reducing the production of these proteins, Warfarin helps to keep the blood flowing smoothly, reducing the risk of clots forming and causing severe complications like strokes and heart attacks.

Potential Side Effects of Warfarin

While Warfarin is effective in preventing blood clots, it can also cause side effects. It is essential to monitor its use carefully and check blood levels regularly to ensure the correct dosage. Here are some potential side effects of taking Warfarin daily:

  • Bleeding: Increased risk of bleeding, including nosebleeds, bleeding gums, or prolonged bleeding from cuts, needles, or intravenous therapies.
  • Bruising: Easy bruising or bruises that appear without an apparent cause.
  • Gastrointestinal issues: Nausea, vomiting, diarrhea, or abdominal pain.
  • Hair loss: Thinning hair or hair loss in some individuals.
  • Skin rashes: Allergic reactions that can cause rashes or itching.
  • Fatigue: Feeling unusually tired or weak.
  • Headaches: Frequent or severe headaches.
  • Dizziness: Lightheadedness or dizziness, especially when standing up quickly.

If you are prescribed Warfarin, follow the instructions from your provider closely and attend regular check-ups to monitor its effects and adjust the dosage if necessary. Additionally, inform your healthcare team about any other medications or supplements you are taking, as these can interact with Warfarin and affect its efficacy.


Heparin is an anticoagulant, or blood thinner, often used to prevent and treat blood clots. It is beneficial for patients undergoing surgery, those with certain medical conditions that increase the risk of clotting, or those who have experienced a heart attack or pulmonary embolism.

How Heparin Works

Heparin enhances the activity of a natural substance in the body called antithrombin III. Antithrombin III helps to deactivate several enzymes involved in the blood clotting process. By increasing the effectiveness of antithrombin III, Heparin prevents the formation of new clots. It stops existing clots from growing larger, ensuring smoother blood flow and reducing the risk of serious complications such as strokes, heart attacks, or blockages in blood vessels in the lungs.

Potential Side Effects of Heparin

While Heparin effectively manages blood clots, it can cause side effects. Regular monitoring by healthcare providers is important to ensure safe and effective use. Here are some potential side effects of taking Heparin daily:

  • Bleeding: Increased risk of bleeding, including internal bleeding, which can be severe.
  • Bruising: Easy bruising or bruises that appear without an apparent cause.
  • Thrombocytopenia: A decrease in platelets, which are cells that help blood clot.
  • Allergic reactions: Reactions that can cause hives, itching, or more severe symptoms like difficulty breathing.
  • Osteoporosis: Weakened bones with long-term use.
  • Injection site reactions: Pain, redness, or irritation at the site where Heparin is injected.
  • Elevated liver enzymes: Changes in liver function tests.
  • Hyperkalemia: High levels of potassium in the blood can affect heart function.

Heparin is usually administered in a hospital where patients can be closely monitored. If you are prescribed Heparin, following your healthcare provider’s instructions and reporting any unusual symptoms immediately is critical. Regular blood tests will be necessary to monitor its effects and adjust the dosage.


Aspirin, also known as acetylsalicylic acid, is commonly used for its anti-inflammatory, analgesic (pain-relieving), and antipyretic (fever-reducing) properties. Low doses of Aspirin, used as a daily blood thinner, may prevent blood clots.

How Aspirin Works as a Blood Thinner

Aspirin inhibits the function of platelets, which are small cell fragments in the blood that play a crucial role in clot formation. It does this by blocking an enzyme called cyclooxygenase (COX). There are two primary forms of this enzyme: COX-1 and COX-2. AspirinAspirin’sthinning effects primarily involve COX-1. Here’s Here’s works:

  1. Inhibition of COX-1: Aspirin irreversibly inhibits COX-1 in platelets. COX-1 produces thromboxane A2, which promotes platelet aggregation (clumping together) and vasoconstriction (narrowing of blood vessels).
  2. Reduced Platelet Aggregation: Aspirin inhibits COX-1 and produces thromboxane A2, decreasing platelet aggregation. This makes it less likely for platelets to form clots.
  3. Long-lasting Effect: Since platelets cannot produce new COX-1 enzymes, AspirAspirin’sirin’sts 7-10 days.

Side Effects and Potential Risks of Using Aspirin Daily for Blood Clotting

While Aspirin is beneficial, it carries several side effects and potential risks, mainly when used daily over long periods. The primary side effect or risk is to the stomach lining; it can cause peptic ulcers and gastritis.

Asprin may also increase the risk of bleeding in the gastrointestinal tract and other body areas, including the brain. When bleeding in the brain occurs, a patient has a higher risk of hemorrhagic stroke. Other patients can have hypersensitivity to Aspirin, such as an allergic reaction that causes hives, breathing problems, and swelling.

Long-term use can impair kidney function. Some patients may develop tinnitus caused by high doses of Aspirin, and children and teens may have a higher risk of developing Reye’s Syndrome, a rare disease that affects the liver and brain.

Aspirin is a valuable daily blood thinner for preventing blood clots, which can significantly reduce the risk of heart attacks and strokes. However, its use must be carefully monitored due to potential side effects and risks.

Does Medical Marijuana Possess Blood Thinning Capabilities?

Marijuana is densely packed with phytocannabinoids that pose various physiological benefits, including blood thinning. However, given the currently limited data, modern research is limited in knowing the exact mechanisms for its anticoagulant properties.

In one study, researchers observed the anticoagulative effects of marijuana extracts on obese rodents. Research revealed that three significant cannabinoids, specifically tetrahydrocannabinol (THC), cannabidiol (CBD), and cannabinol (CBN), inhibit blood clot formation. Furthermore, CBD affects thrombin, an enzyme that converts fibrinogen to fibrin, triggering blood clotting activity.

Is It Safe To Use Cannabis and Blood Thinners?

Medical marijuana contains compounds, such as THC and CBD, which have various effects on the body. There is some evidence suggesting that marijuana might have mild blood-thinning properties. This means it could potentially affect how blood clots form.

Cannabis can increase the risk of dangerous side effects for patients taking Warfarin. Still, one study in 2023 suggested that medical marijuana may not conflict with other types of blood thinner medications. However, the blood-thinning effects of marijuana are not well understood or extensively studied.

Some research indicates that marijuana might slightly affect platelets, the blood cells involved in clotting. This could mean that marijuana might increase the risk of bleeding for some people, especially if they are also taking other blood-thinning medications.

Does Cannabis Interact with Blood Thinners?

Despite the anticoagulation properties of cannabis, the big question remains— cannabis and blood thinners: how do they react? Current data tells us that combining marijuana and blood thinners has adverse effects.

First, the human liver is the frontline defense that metabolizes, filters and detoxifies all the drugs and substances we take. Combining various substances can alter liver functions, which can, in extreme cases, result in harmful drug interactions.

Secondly, a study examining the effects of cannabis and Warfarin (an anticoagulant) showed that their combination elevates INR values beyond normal. That means the blood-thinning impact is amplified, and blood clotting occurs significantly slower than usual, resulting in bleeding. As a result, the medical community feels mixing cannabis and blood thinners to be generally unsafe.

Is Medical Cannabis Right For You?

You must consult regularly with a healthcare provider if you have severe underlying health conditions. Prescription blood thinners can be contraindicated (conflict) with cannabis and reduce the efficacy of the medication. That can increase your risk of developing life-threatening blood clotting.

If you do not have a medical cannabis card but believe you need one, we can help. Visit this link to check the qualifying conditions for medical marijuana treatment. Medwell Health offers medical marijuana certification in Massachusetts with caring, compassionate practitioners who are cannabis healthcare experts. Schedule your appointment now!

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