<s>[INST] My Mother takes warfarin because of blood clots in her lungs, they say they have her medicine regulated now and said to come back in two months, the longest perios of time she has gone without checking her blood.  What signs would tell us her blood is thickening and needs to be checked again? [/INST] Hello,I'm afraid there is no sign that warfarin effect has decreased. The opposite is easy... If she's taken too much warfarin, it can become apparent but less than enough warfarin is not easy (or possible) to detect without laboratory tests.If she's having stable values of INR the last times she's checked then she'll likely be OK. If the INR has been fluctuating then she has to check it sooner.Potential reasons for INR variation include infections, changes in diet, adding new drugs to your regimen etc.I hope I've helped!If you need more information on this subject, please let me know.Kind Regards! </s>