Oral warfarin is routinely required for anticoagulation therapy after heart valve surgery. However, the dosage of warfarin is often difficult to control because of individual differences. Patients are often frustrated when they are told that their blood draw was normal a few days ago, but why are they told that their blood draw was abnormal this time? Simply put, after valve replacement, the blood will clot when it encounters the foreign body of the prosthetic valve, and we use warfarin as an anticoagulant to keep the blood from clotting and creating a blood clot. Currently, there is no alternative to warfarin. Each person absorbs and tolerates warfarin differently, just as each person has a different amount of alcohol. Some people are genetically insensitive to warfarin because of their genotype, and others can take one tablet to meet the standard, while others need to take 2-3 tablets. For the average person with a normal genotype, height and weight are among the factors that affect warfarin dosage. A person with a height of 180 cm and a weight of 80 kg will definitely take a different amount of warfarin than a person with a height of 150 cm and a weight of 40 kg. Warfarin is metabolized by the liver, so many drugs and foods that are metabolized by the liver can affect it (see “How to administer anticoagulation therapy after heart valve surgery”). In daily life, it may often happen that a blood test for coagulation is normal, but after taking a herbal medicine or eating animal liver, another blood test indicates abnormal coagulation, and the INR is either too high or too low. This requires the patient to be abstinent: to know what not to eat and to strictly enforce it. Whatever the cause of the substandard coagulation, it is ultimately resolved by adjusting the warfarin dosage. The process of adjusting warfarin dosage is often another headache for the majority of patients. We often encounter patients who do not meet the standard after several months of adjustment. Here is how to adjust: First, you must stay away from foods and drugs that may affect the effectiveness of warfarin. Chinese herbs, pork liver, these things are better known to patients. But often people ignore some for example: Chinese medicine, bruising medicine (for external use), multivitamin tablets containing vitamin K. When abnormalities occur, we should first examine whether we have these ingredients around us and whether we have used these things. Staying away from them in a timely manner is the first thing that needs to be done. The next thing is to adjust the dosage of warfarin. Generally, imported warfarin is 3mg/tablet and domestic warfarin is 2.5mg/tablet. Take imported warfarin as an example: we are better to adjust the dosage: 0.75mg (1/4 tablet); 1mg (1/3 tablet); 1.5mg (half tablet); 2mg (2/3 tablet) 2.25mg (3/4 tablet). Coagulation function was judged by the international standard ratio (international standard ratio, INR). When its value is less than 1.8, that means the anticoagulation strength is not enough and warfarin is taken less; when its value is more than 2.5, that means the anticoagulation strength is too strong and warfarin is taken too much; if it is between 1.8 and 2.5, then congratulations, the anticoagulation is appropriate and there is no need to adjust the dosage of warfarin. When the anticoagulation strength is not enough, we need to increase the dosage of warfarin, it is generally recommended not to increase too much suddenly, it is advisable to slowly increase the dosage of 0.75mg (1/4 tablet). For example, if you originally took 1 tablet orally every day and the INR was 1.50 when you drew blood, increase 0.75mg (1/4 tablet) daily to 3.75mg (1+1/4 tablet) and review again after about 1 week of oral intake. When the anticoagulation intensity is too high, we reduce the dosage of warfarin, again it is recommended not to reduce too fast, it is advisable to reduce the dosage of 0.75mg (1/4 tablet). For example, if you take 1 tablet orally every day and the INR is 2.90, reduce the dosage by 0.75mg (1/4 tablet) daily to 2.25mg (3/4 tablet) and recheck after about 1 week of oral intake. It is important to note that if the INR exceeds 3.0, oral warfarin needs to be stopped immediately and the patient is advised to seek immediate medical attention. This is because if the INR is too high it indicates extremely poor coagulation and may lead to life-threatening bleeding due to intracranial bleeding or bleeding from other parts of the body. Sometimes the oral administration of warfarin is not as simple as described above, for example, 2.25mg (3/4 tablet) per day and a blood draw indicates that the INR is too low, and once it is increased to 3mg (1 tablet), the blood draw indicates that the INR is too high; in this case, the method of taking warfarin in intervals can be used. That is, the first day oral 2.25mg (3/4 tablets), the second day oral 3mg (1 tablet), the third day and then oral 2.25mg (3/4 tablets) so that the alternating cycle of taking drugs. Warfarin is such a “pain in the ass”, but once you get the hang of it, it’s easy to keep your clotting function within normal limits.