How can you self-manage and adjust anticoagulants in the long term?

Anti-clotting tablets (oral anticoagulants) are used to stop the blood from clotting too quickly. The aim is to lower the risk of cardiovascular (heart and blood vessel) diseases, especially strokes. They are often prescribed for people who have atrial fibrillation, artificial heart valves or people who have had pulmonary embolism.

Various anticoagulant tablets are available. Vitamin K antagonists are commonly used. They’re also known as coumarins. In Germany, the most frequently used drug from that group is phenprocoumon. It is best known under the trade name Marcumar, but also as Falithrom and Phenprogramma.

Vitamin K antagonists slow down the blood-clotting process. The clotting ability of the blood has to be monitored regularly in order to adapt the dose of the medication if necessary: It should be high enough to prevent blood clots – but low enough to minimize the risk of serious bleeding.

How is the clotting ability of blood measured?

People who are on vitamin K antagonists usually have the clotting ability of their blood checked regularly. For this purpose, a blood sample is taken and the INR value (international normalized ratio) is measured. The INR value reflects the blood-clotting speed.

An INR around 1 is considered to be normal in people who are not taking anticoagulant medication. This value is higher in people who are taking anticoagulant medication because it takes longer for their blood to clot. An INR value of “2,” for example, means that the blood takes twice as long to clot. Different people may have different target INR values, mainly depending on their underlying medical condition.

The blood's clotting ability is first measured on the third day of taking the anticoagulants. That's how long it takes for the medication to start working. This blood test is done a few times per week at first. If the INR value hardly changes over several consecutive measurements, the blood tests can be done less frequently. If the target value is maintained over several months, it’s enough to then only check the values every four weeks.

The target INR range for people with is generally between 2 and 3. If the value is higher (e.g. 3.5) the drug dose is reduced. If it is lower (e.g. 1.5) the dose is increased a bit. Because the medication doesn't work immediately, it generally takes a few days for the INR value to change.

How can you check your blood yourself?

You don't always have to go to the doctor to have your blood tested. Instead, you can attend a patient education class to learn how to measure your INR values on your own. If the patient education is prescribed by a doctor, statutory health insurers usually cover the costs (in Germany). It makes sense to ask your health insurer about this beforehand. This kind of patient education is offered by doctor's practices and hospitals, for instance.

To monitor your blood values yourself, you simply have to prick your finger and smear a drop of blood onto a test strip. The test strip is then inserted into a special device that measures the INR value.

You are also shown how to adjust your dose yourself. People who monitor their blood's clotting ability themselves only have to go to the doctor's every few months.

The patient education doesn't only teach you how to monitor your own blood and adjust your medication. It also provides important information about many other aspects of treatment, like how your diet can influence your blood's clotting speed, interactions with other medications, and what you have to bear in mind if you're going to have an operation and are taking anticoagulants.

Many people who take anticoagulants prefer to self-monitor because it means that they're more flexible and have fewer check-ups at the doctor's. Studies have also shown that people who monitor their own blood are less likely to develop blood clots and resulting complications.

Some people are hesitant to monitor their own blood. Others aren't able to, for instance because they have poor vision. Then they can ask loved ones to help. Patient education classes to learn how to monitor blood and adjust medication can also be attended by loved ones.

IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Please note that we do not provide individual advice on matters of health. You can read about where to find help and support in Germany in our information “How can I find self-help groups and information centers?

Updated on January 29, 2021
Next planned update: 2024


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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