There are some signs as to blood clots in the vein of the leg like swelling and pain. And there are certain things in the history that can be suspicious for a clotting disorder problem such as family history of blood clots in the veins of the lungs or in the legs, recurrent miscarriages, strokes at early eages. But as to diagnosing yourself with a fresh new blood clot in a vein or artery somewhere, unless you are an ultrasound tech with a home machine then, no.
As for diagnosing yourself with a stroke, weakness or sensory changes on one side of the body, vision or speech changes, as well as any other sudden neurologic change that affects one side of the body (sometimes both in more complex cases) are all possible presentations of a stroke. WIth numbness on one side of the face, there may be accompanying numbness of the body on th same side as well as weakness of the smile on that side. Check the mirror. If you have a history of heart disease, cholesterol problems, diabetes, or tobacco history you may need to start with your primary care physician. GOod luck.
terk: Being a stroke survivor of 2 CVA's to the basial ganglia cuadate head within the past 6 months (last one 9/20/02), I'd say it would be darn near impossible to self-diagnose if you had a blood clot hidden in your vascular system. But there are other signs and indicators that say your at just as much risk, that is hypertension or high blood pressure or high cholesterol. The biggest risk is NOT knowing what those are? The new word for stroke is "brain attack". You know what a heart attack is, a brain attack is the same thing, it just happens in your brain instead of your heart, but they cannot by-pass an artery in your brain by taking one from your leg.
Numbness in your lip, cheek, arm, leg favoring one side are possible and serious signs of a pending TIA/stroke. TIA is the same thing as a stroke only difference is it doesn't leave permanent damage like a CVA/stroke. That numbness is your body telling you there is a blockage somewhere. My recommendation if your having numbness to your face and side to see your doctor immediately, if possible see a Cardiologist as there are many heart ailments that can lead to stroke. If its just lips/face, and you have teeth pain, it could also be dental related. IF your BP is over 130/85 get to your Doctor and get it under control. Don't mess/ignore with that numbness, ignore it a week and you can end up completely disabled.