Do Blood Thinners Make You Tired?

Heart attack and stroke are life-threatening medical conditions that everyone is aware of. Heart disease is a leading cause of death in the U.S.; every year, 805,000 people have a heart attack, and in addition, 795,000 have a stroke.

A heart attack happens again in 200,000 people annually, while about 185,000 people, or nearly every fourth, will have a stroke again. (1-2) Medications called blood thinners can prevent another stroke or heart attack.

For these and other medical conditions or after surgery and immobility, blood thinners protect the body from dangerous blood clots that can be life-threatening. The positive effects have been clinically proven already. However, some patients might feel tired or dizzy while taking the medication. At first, this seems acceptable and self-manageable, yet it may signal the need for medical care.

This article explains these and other blood thinners’ possible side effects that can be serious. Keep reading to understand how blood thinners work, what you should do in case of an adverse event, and the daily practices that will help you live a safe life while on the treatment without fear.

Why Would One Need Blood Thinners?

Blood thinners are medications that don’t thin the blood. These medications, better explained as clot-preventing drugs, protect the body from dangerous blood clots.

Good and Dangerous Blood Clots

Blood clots form when an injury occurs, and the bleeding should be stopped. The damaged cells send signals for making clots from blood cells, platelets (cell fragments), and fibrin (a protein) at the place of injury. The spleen gets the signal and releases platelets that travel to the wound within the bloodstream. (3)

Platelets put the damaged sides closer to repair and activate fibrin. Fibrin is a long and sticky protein that forms a fibrin clot which aims to hold blood cells. This is how good blood clots are formed in healthy individuals and protect the body from bleeding to death.

In other cases, the body makes abnormally more blood clots than needed or where they shouldn’t be formed. These blood clots can be dangerous when they come in: (4)

Deep veins (deep vein thrombosis-DVT) in the lower leg, thigh, or pelvis. Clots can block the vein and damage the leg;

Lungs (pulmonary embolism) from the leg; there, a clot can get stuck in an artery. This can damage the lung tissues, and the body will not get oxygen as needed;

Brain, where blood clots can block or plug a blood vessel (ischemic stroke) or a blood vessel breaks and cause bleeding (hemorrhagic stroke); (5) (6)

Heart and blocks the blood flow to the heart (heart attack); (7)

Kidney and cause kidney problems and failure. (8)

Blood clots can happen to anyone and are the reason for 100,000 deaths in the U.S. each year. (9)

Anticoagulants and Antiplatelet Drugs

Blood clots are often preventable, and early diagnosis is critical. Medications that can prevent the body from the described serious and life-threatening conditions are blood thinners or anti-clotting medications, and Harvard Medical School divides them into two main groups:

Anticoagulant drugs – these medications don’t allow formed clots to grow bigger or delay the process of blood clotting. Some of the anticoagulants are:

  • Apixaban (Eliquis);
  • Dabigatran (Pradaxa);
  • Edoxaban (Savaysa);
  • Rivaroxaban (Xarelto);
  • Warfarin (Coumadin);
  • Enoxaparin (Clexane);
  • Heparin.

Anticoagulants are prescribed to patients with artificial heart valves, irregular heartbeat, those who had a heart attack, have heart diseases, or are at risk of developing blood clots (hip or knee replacement).

Antiplatelet drugs – this group of medication prevents forming clots in a way that keeps platelets from sticking together. Some of the antiplatelet medications you already know:

  • Aspirin;
  • Clopidogrel (Plavix);
  • Prasugrel (Effient);
  • Ticagrelor (Brilinta):
  • Dipyridamole (Persantine);
  • Abciximab (ReoPro);
  • Tirofiban (Aggrasat);
  • Cilostazol (Pletal);
  • Vorapaxar (Zontivity).

Antiplatelet drugs are used to prevent the recurrence of blood clots after a heart attack or stroke. (10-11)

Blood Thinners Side Effects You Should Take Serious

Patients who use blood thinners may experience side effects, as with any medication. Bleeding can be a serious side effect described in the warning of the many blood thinners’ Medication guide. However, these medicines have other known side effects, some of them serious too, and require medical care immediately.

Do Blood Thinners Make You Tired

Do Blood Thinners Make You Tired – Blood Thinners Side Effects You Should Take Serious

Tiredness, Dizziness, or Weakness Can Be Serious

Feeling tired, lack of energy, dizzy or weak are side effects known for blood thinners. People describe dizziness as feeling faint, lightheadedness, feeling of floating, losing balance, or having a false sense of motion.

These effects may limit your ability for daily activities but, at the same time, can be a sign of anemia. Therefore, if you are in therapy and feel some of those, drug manufacturers recommend you call your doctor.

The side effects have been reported with various frequencies and severities. People who have a history of heart attack or ischemic stroke and use aspirin or/and clopidogrel to reduce the risk might feel tired, yet the frequency of this effect is not known. (12-13)

In patients who use other antiplatelet drugs such as heparin, warfarin, or prasugrel, feeling tired can be serious, so they need to call the doctor immediately and get medical help. (14-16)

Dizziness or weakness has been reported as a side effect of many blood thinners. If you use apixaban, dabigatran, rivaroxaban, betrixaban, or prasugrel and have one or both of these side effects, you should call your doctor or get medical help right away. (16-20)

If you are using one of these medications and feel dizzy while you stand up, sit down and stay there until you feel better. When you are getting up, do it very slowly. If you feel dizzy, first lie down, sit after and wait to feel better and not faint. Before you feel good again, don’t drive or operate with machines or tools. (21-22)

These side effects could increase the risk of falling, breaking a leg or arm, or getting injured and bleeding in your body. Even minor trauma can be severe for a patient on a blood thinner because the body’s reaction to stop bleeding does not work as usual.

Risk of Bleeding

So, excessive bleeding is a common risk when using anticoagulants and antiplatelet therapy. These drugs are prescribed to prevent forming clots, which include the good ones. If you cut, the bleeding will take more time than usual. Internal bleeding or a sudden hit to the head can be very dangerous, so you need to call a doctor immediately.

You need immediate medical care if you notice bruising, see blood in your urine or stool, vomit, or cough up blood.

The aim of every doctor with clot-preventing drugs is “to find the right balance between helpful and harmful clotting,” as Dr. Gregory Piazza, associate professor of medicine at Harvard Medical School, explains. (25)

Can Blood Thinners Make You Cold?

Relationship Between Blood Thinners and Body Temperature

It is interesting whether blood thinners can make individuals feel cold or not. There is only one research study that evaluated the sensation of feeling cold and the use of blood thinners, but the evidence is inconclusive. However, many factors may contribute to feeling cold while on blood thinners. Everyone is not susceptible to this situation, and individual responses can vary according to the available data.

It is crucial to understand that every person’s response might differ. If one experiences shivers while on these medications, it does not necessarily imply others will go through the same side effect.

What Does the Research Say?

One study evaluated the relationship between feeling cold and using blood thinners. J. L. Burton and P. Pennock conducted this study in 1979. They found that people on blood thinners reported feelings of coldness (26). Unfortunately, though, no additional investigations have been carried out since then.

It is essential to mention that research studies have yet to discover if there is any relationship between blood thinners and feeling cold. This may be due to the fact that most of the studies evaluate the risk of bleeding (which is the major side effect of these drugs) and their efficacy in clot prevention. So, it is challenging to find out whether they interfere with the thermal regulation of the body or not due to a lack of scientific evidence and limited studies.

Factors That Can Affect People’s Perception of Cold

There are several factors that affect the perception of cold in different people. These include:


The sensation of cold (as well as warmth) declines in the body with increasing age. This may be attributed to the diminished blood flow in the peripheral nerves and a decrease in the number of nerve fibers as we age. (27)


Although most of the studies have shown similar cold perception in both males and females, there are some studies that show increased cold intolerance in females as compared to males. Females are considered to have a lower threshold for cold and can sense temperature changes better than males. (27)

Body fat:

Higher body fat is considered to provide insulation against the cold environment. Hence, people who are overweight have a higher threshold for cold perception. However, long-term studies have shown fewer differences in cold perception between overweight and lean people. (28)

Each person’s perception of being chilled when taking anticoagulants proves complex and multifaceted. Other variables, including temperature thresholds of individual patients, interactions with other medications, personal overall health status, or even colder climate changes, may equally play a part.

In case these sensations persist and cause distress, it is recommended that individuals report their medical concerns promptly to their healthcare professionals.

How to Manage the Feeling of Cold While on Blood Thinners?

Several strategies may help to improve comfort and maintain body warmth if you feel cold while on blood thinners. They may include (29):

  • Wear appropriate clothing.
  • Use heating methods.
  • Stay active and do regular exercise.
  • Maintain a comfortable room temperature.
  • Stay hydrated.
  • Protect extremities.
  • Practice relaxation techniques.
  • Consult with your physician.

Talk To Your Doctor About Side Effects

Heavier menstrual bleeding, red or brown urine, or bleeding from gums that don’t stop quickly are other signs of possible side effects of blood thinners. Learn about the side effects that you could expect from the prescribed drug. Ask your doctor or pharmacist for more information.

In case you experience an adverse event, call your doctor. The doctor will know better if the event is associated with the drug and will know if any changes are required for your therapy.

You may report side effects to the Food and Drug Administration and contribute to drug safety for all patients. Reporting will help the health authorities to know better if those described are in the known range, more or less frequent, or if any other undescribed side effect could be linked with the medication.

A Life with Blood Thinners

With the blood thinner prescription, your doctor has probably given you recommendations to stay safe and live life as much as before. The Agency for Healthcare Research and Quality advice patients on blood thinners to:

Take medicine as directed – if you miss a dose, take it ASAP and never take a double dose;

Talk to your doctor if you use any other medication – if you take medicine already or if you need to start with a new one, talk with the pharmacist, other doctors, and your dentist. Blood thinners can interact with certain medicines; some should not be taken together, or the dose should be adopted;

Talk to your doctor before using over-the-counter (OTC) medicines – some OTC pain relievers (ibuprofen or naproxen), cold medicines, multi-vitamins, or herbal products contain ingredients that can increase the risk of heavy bleeding and should not be used together,

Prevent injuries – have physical activities with less risk of falling (walking or swimming), wear gloves when gardening, use knives and scissors carefully, use a soft toothbrush, and carefully trim toenails;

Vitamin K – affects the warfarin effect and prolongs the time for forming a clot. Broccoli, asparagus, cauliflower, spinach, and parsley are rich in vitamin K, and increased intake can affect the warfarin treatment;

Do blood tests as directed – tests are needed to check how blood is clotting;

Avoid alcohol (30)

Bring Back Your Life to Normal

Knowing the facts about blood thinners’ side effects is not a reason for fear. Anti-clotting medications prevent stroke, heart attack, or pulmonary embolism and can save your life. When the right balance between helpful and harmful clotting is achieved, you are protected from bad clots and should not be overly worried about intense bleeding.

Your role in this treatment is crucial. Learn about the medicine you take and be aware of any changes that might appear. If you notice some warning signals, such as dizziness, weakness, or tiredness, but also bleeding from gums, nose, or bruising more easily, call your doctor.

Follow your doctor’s recommendations for medication usage and implement advice for a daily routine. Use your lifesaver medication properly, be careful with your activities, and you will return to everyday life and enjoy it.

See Also

Is Ibuprofen a Blood Thinner?

Do Blood Thinners Decrease Blood Pressure?

Do Blood Thinners Affect Oxygen Levels?

What is the Creatinine Level in Blood Tests?

Is Amoxicillin Good for UTI?

Current Version
November 29, 2022
Written By
Biljana Srbinovska, MPharm
August 14, 2023
Medically Reviewed By
Franco Cuevas, MD
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