DVT Blood Thinner Complications

Medically Reviewed by Carmelita Swiner, MD on April 30, 2022
5 min read

If you have deep vein thrombosis (DVT), your doctor may want you to take blood thinners. These do a good job to keep your blood moving smoothly through your veins and arteries. But they also can cause possible side effects. The most worrisome one is bleeding. Because of this, your doctor will want you to take certain precautions. Here’s what you need to know

The most common medications to take for DVT are anticoagulants, or blood thinners. They prevent clots from getting bigger. They also reduce your risk of developing more clots.

Blood thinners can be taken by mouth, given by IV, or by an under-skin injection. The drug Heparin is given by IV. The most commonly used injectable blood thinners to treat DVT are enoxaparin (Lovenox) and fondaparinux (Arixtra).

Once you take an injectable blood thinner for a few days, your doctor will most likely switch you to a pill that you swallow. Common ones are warfarin (Jantoven) and dabigatran (Pradaxa).

Certain blood thinner medications don’t require an IV or injection. Three common pills are apixaban (Eliquis), edoxaban (Savaysa), and rivaroxaban (Xarelto). These can be given by mouth, as soon as you are diagnosed.

You may need to take your blood thinner medications for at least 3 months. It is very important that you take them exactly as prescribed, in order to prevent serious side effects. If you take warfarin, you will need to take regular blood tests to check how long it takes your blood to clot. Pregnant women also need to avoid certain blood-thinning drugs.

Blood thinners actually thin your blood, which makes your blood harder to clot. That means if you cut yourself, or have an injury, it’s harder to stop the bleeding. Specific blood thinners can also cause certain problems:

Warfarin. This drug has a much higher risk of causing bleeding than other blood thinners because it requires a precise dosage. It is usually prescribed when clots form in the blood vessels in your arms, legs, or fatty tissue like your breasts, butt, or thighs. These clots block blood flow and cause areas of your skin to die. This side effect is usually seen within 5 to 10 days of starting warfarin. Other side effects include blue or purple toes and feet, and miscarriages, which is why it’s not recommended in pregnancy.

Heparin. This drug can actually cause a condition called thrombocytopenia, also called HIT. There are two types: one, known as Type I HIT, is more common and happens to about 10% of people on heparin. The condition causes a slight decrease in your platelets, a type of blood cell that helps your blood to clot. It resolves within about a week once you stop the drug.

Type 2 HIT is more serious. It triggers your immune response to activate platelets and can cause widespread clotting in your body. This side effect happens in about 1 in 100 people who take heparin. If your doctor suspects either, they will immediately switch you to another drug.

The risk of bleeding depends on which drug you are on. About 2% of patients on heparin experience major bleeding. People who take warfarin have anywhere from 0.4% to 7.2% risk of major bleeding, and up to a 15% chance of a minor bleed. If you take one of the newer oral anticoagulants, the risk is less.

You can reduce your risk of blood thinner complications if you make sure that you always take your blood thinner as directed. This may involve:

  • Check if your blood thinner needs to be taken at the same time of day, every day.
  • Don’t skip a dose.
  • Never take a double dose.
  • If you miss a dose, take it as soon as you remember. If you don’t remember until the next day, call your doctor’s office right away for instructions. If they are not available, skip the missed dose and start again the next day. Mark the missed dose in a calendar and let your doctor know.
  • If it’s hard for you to remember to take your pill every day, use a pillbox with a slot for each day to help you keep track of your medicines.

One thing that may raise your risk of blood thinner complications is if you take them with certain other medications or supplements. It is very important that you let your doctor know about every other medicine you take, even over-the-counter ones, vitamins, and herbal products. These medicines may change the way your blood thinner works, and vice versa.

You also need to check the products carefully to make sure that they do not contain aspirin. This drug may make it harder for your blood to form clots. As a result, you may be at higher risk of bleeding if you are also taking a blood thinner. Always talk to your doctor before you use any medication that has aspirin in it.

Other over-the-counter medications may also interact with your blood thinner. The most common ones are pain relievers, cold medicines, and stomach remedies. Vitamins and herbal products may also interact with blood thinners, including multivitamins, garlic, ginkgo biloba, and green tea.

It’s also very important that you let all your doctors know -- even ones that you see for different problems -- that you are taking a blood thinner. You should also let your dentist and pharmacist know, as well. Blood thinners may interact with medicines and treatments that other health care professionals prescribe. If they want to start you on a new drug, let the doctor who manages you on your blood thinner know. They may need to change your dose.

You may also need to make changes to your diet. This may include:

  • Avoid alcohol.
  • Limit Vitamin K if you take warfarin. High amounts of vitamin K can work against this drug. You can go to www.usda.gov and search for a list of foods that contain vitamin K. Other blood thinners are not affected by vitamin K.
  • Keep an eye on stomach issues. If you are unable to eat or keep food down due to vomiting or diarrhea, let your doctor know if it lasts more than 24 hours. It could impact your blood thinner dose.

You will need to call your doctor right away if you notice any of the following:

  • Heavy menstrual bleeding
  • Red or brown urine
  • Red or tarry bowel movements
  • Bleeding from the gums or nose
  • Brown or red vomit
  • Coughing up blood
  • Severe head or stomach pain
  • Unusual bruising
  • A cut that won’t stop bleeding
  • A serious fall or bump on the head
  • Dizziness or weakness

These could all indicate abnormal bleeding.