Is your cholesterol under 200?  Or is that even the right question to ask anymore? We've learned a lot about cholesterol in the past few decades, and it can be hard to understand and follow all the different advice out there. Here's how I simplify things.

We have known for a long time that high cholesterol causes plaque inside arteries (called atherosclerosis). As the plaque builds up, the arteries get narrower and less blood can get through. That can cause heart attacks, strokes, and problems in other parts of the body.

Now, we also know that not all types of cholesterol are equally bad. The cholesterol responsible for those plaques is primarily LDL (low-density lipoprotein), the so-called "bad" cholesterol. Triglycerides (the building blocks of fat) build up in there, too. HDL (high-density lipoprotein), on the other hand, is a "good" form of cholesterol, and higher levels can help reduce atherosclerosis. A simple way to remember this is that you want your LDL to be low and your HDL to be high.

What about total cholesterol? Your total measured cholesterol is made up primarily of LDL, HDL, and triglycerides. There are other components, but these are the three main factors. LDL cholesterol is difficult to measure directly, and is usually calculated using the following formula:

LDL = [Total cholesterol] - [HDL] - [Triglycerides ÷ 5]

That is, LDL equals your total cholesterol, minus your HDL, minus your triglyceride number after it's been divided by 5.

HDL and total cholesterol are usually pretty constant throughout the day, but triglyceride levels rise sharply after a meal. You must be fasting for at least 6-8 hours to get a true estimate of triglycerides and LDL.

Total cholesterol turns out to be a very poor predictor of risk, because a high or low total doesn't tell you about the LDL, HDL, and triglyceride levels. Some people use the ratio of total and HDL cholesterol to estimate risk, because you don't have to fast to measure those numbers. I prefer to get a fasting blood test and look at LDL, triglycerides, and HDL. If you know those three numbers, the total and ratio don't add any additional information.