You'll live a longer and healthier life when your body mass index (BMI) is under 25. It may be possible to have a full life span with a somewhat higher BMI (25-29) if you stay in good shape, but in no event should you tolerate a BMI over 29. Aiming for 24 should be your goal. The adverse health effects of obesity are multiple and avoidable.
Know your blood glucose (blood sugar level). The consequences of elevated blood glucose are not only eventual plaque formation and narrowing of the blood vessels, particularly the coronary arteries, but also damage to your nerves, kidneys, eyes, and immune system. Millions of people are walking around with diabetes, with its effects already ravaging their bodies. Diabetes is sometimes not detected until something terrible happens, like a heart attack, stroke, or kidney failure. Seize the initiative and have this simple test!
Check your blood pressure early and check it often. Just about every drugstore I walk into has an automated blood pressure monitor, so use it. If your blood pressure is greater than 130/85, bring the information to a physician and take action. High blood pressure is a silent killer. You can feel great right up until the moment you die; I see this virtually every day. Hypertension is one of the leading cause of kidney failure (being on dialysis is no fun), and causes enlargement of the heart, accelerated atherosclerosis in your arteries, and sudden hemorrhages in the brain (hemorrhagic stroke), all of which can have sudden death as their first symptom.
The last numbers that are essential to know are your lipid profile: total cholesterol, LDL cholesterol (the bad one, which should be low), and HDL cholesterol (the good one, which should be high). Heart disease, particularly due to atherosclerotic plaque buildup (narrowed coronary arteries), and ischemic strokes are major causes of premature death. Cholesterol-lowering drugs are a major success story in modern medicine. They're inexpensive, well tolerated, and extremely effective. Take advantage of this great medical advance.