1. Standard blood sampling is performed in the morning, on an empty stomach (no less than 8 to 12 hours after last meal).
2. Drinking alcohol (including beer) is forbidden.
3. Physical loads or extensive work is not recommended.
4. It is strictly forbidden to smoke on the day of sampling since nicotine is a toxin which damages blood vessels and affects hemostastis substantially.
5. It is preferable to refrain from taking any medicinal products that affect blood clotting -- above all, this is true for indirect (acetylsalicylic acid) and direct (heparin) anticoagulants.
6. It is also recommended to refrain from taking pharmaceuticals that increase hemostatic activity (oral contraceptives, hormonal drugs, etc.).
7. Blood sampling during menstruation is not performed.
8. When collecting blood samples for the INR test from patients taking warfarin and other indirect anticoagulants:
   - sampling for the INR test, as well as administration of pharmaceuticals, is performed in accordance with a strict schedule: every day during dosage selection -- usually this takes 10 to 14 days (if the dose is correct, the INR value should be 2 to 3), and two to three weeks afterwards.

Some indications to an unscheduled INR change are:

• protracted cold or an acute infectious process;
• a need to adjust therapy of concomitant disorders;
• a change of climate (flying or moving to a long distance);
• changes in the diet, work and rest pattern or physical loads;
• bleeding (from the nose or gums, or excessive menstruation), prolonged bleeding following minor skin damage;
• appearance of blood in feces, urine, sputum or vomit matter;
• during anticoagultion therapy -- pain in joints accompanied by swelling and lumpiness.

Individuals that depend on blood thinning pharmaceuticals shall always remember that any change in their life is a good reason to have an International Normalization Ratio (INR) test taken.