This blog provides basic information on health in simple english for lay people.

Tuesday, April 15, 2008

What do my cholesterol results mean?

You've probably had your cholesterol levels checked, or could very easily - it just takes a blood test. But what do these numbers mean, and what are they supposed to be?

Types of cholesterol measured:
Well, naturally you'd think that a lab test for cholesterol would simply tell you how much cholesterol you have. And it does, but wait: There are several cholesterol measurements. These are:

Total cholesterol.
HDL cholesterol.
LDL cholesterol.

Total cholesterol:
HDL cholesterol is the "good" cholesterol carried on high-density lipoproteins. Having more of it means you're more likely to have a lower risk of coronary heart disease (CHD).

LDL cholesterol is the "bad" cholesterol carried on low-density lipoproteins. You're better off with lower levels of LDL cholesterol, because it's associated with a higher risk of heart disease.
Note that total cholesterol doesn't equal HDL cholesterol plus LDL cholesterol. This is because there are still more types of cholesterol, which we won't talk about here.

Your cholesterol numbers:
Cholesterol is measured as milligrams of cholesterol per decilitre of blood, which is abbreviated like this: mg/dL.

Often, your total cholesterol is the only type tested. Or you may have both your total cholesterol and your HDL cholesterol tested at the same time.

If your total cholesterol is:

200 mg/dL or less: Desirable cholesterol level
Between 200 and 239 mg/dL: Borderline high cholesterol level
240 mg/dL or more: Too high

If your HDL cholesterol is:

Less than 40 mg/dL: Too low
More than 40 mg/dL: Beneficial especially if it's above 60 mg/dL

People should have a lipid profile test (total cholesterol, HDL cholesterol and triglycerides) after an overnight fast. These tests allow the LDL cholesterol to be calculated.

Elevated triglycerides are common and a risk factor for CHD. Triglycerides may be elevated even if the total and HDL cholesterol are normal. So there is no way to know if a person has high triglycerides unless it is measured.

If you are 20 years old or older, have no heart disease and your LDL cholesterol is:

Less than 100 mg/dL: Desirable
100 - 129 mg/dL: Near optimal/above optimal
130 - 159 mg/dL: Borderline high
160 - 189 mg/dL: High
190 mg/dL and above: Very high

If you already have CHD or diabetes, then your LDL cholesterol should be 100 mg/dL or less.

Your cholesterol ratio:
Sometimes you'll be given your cholesterol results as a ratio of total cholesterol to HDL cholesterol. (This is the same thing as saying total cholesterol divided by HDL cholesterol.) According to the American Heart Association (AHA), the ratio should be below 5:1 with the optimal amount being 3.5:1 (3.5 to 1).

It's also possible to divide LDL cholesterol by HDL cholesterol to obtain a ratio. (This is the same thing as saying the ratio of LDL cholesterol to HDL cholesterol.) In this case, the ratio should be below 3.5.

However, the AHA recommends using absolute numbers for cholesterol (as discussed above) rather than ratios. The reason is that the absolute numbers give doctors a better idea of what type of treatment is needed by the patient, than do ratios.

Your triglycerides are another fatty substance in the blood that affects your risk for heart disease. Most fat in food, as well as in your body, is present in the form of triglycerides. High levels of triglycerides are a matter of concern and are linked to the risk of heart disease, just as with cholesterol.

If your triglycerides are tested, here is how you can interpret the numbers, according to the Third Report of the Expert Panel on the Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults:

Less than 150 mg/dL: Normal
150 - 199 mg/dL: Borderline
200 - 499 mg/Dl: High
More than 500 mg/Dl: Very high

Calculating LDL cholesterol:
If your triglycerides are less than 400 mg/dL, your doctor can calculate your level of LDL cholesterol from your tested levels of total cholesterol and HDL cholesterol and triglycerides. The equation your doctor might use is:

LDL cholesterol = total cholesterol -- (HDL cholesterol + [triglycerides/5])

Remember, only your doctor should determine the best way to evaluate and interpret your cholesterol levels. Speak to your doctor if you have any questions about your cholesterol levels or the best way, given your unique needs, to reduce your risk for heart disease.


What is Cholesterol and how it affects me?

You've heard about cholesterol and know that you have to "watch it" to stay healthy. But what is cholesterol, and what exactly are you watching?

Cholesterol is a fatty substance that your body needs to function. In fact, it is essential for life. You need cholesterol to form cell membranes, many hormones and bile acids (which digest fat), to name just a few. Without cholesterol, you couldn't live. But, as is so often the case, too much cholesterol can hurt you.

When there's too much cholesterol in your blood, it can build up on the inside walls of your arteries. Over time, the cholesterol build-up, called plaque, can narrow the space for blood to flow through. This can happen in the arteries everywhere in the body but is most dangerous in the arteries that feed the heart and other vital organs.

When plaque build-up narrows the coronary arteries, which supply oxygen-rich blood to the heart, chest pain, shortness of breath and other symptoms of coronary heart disease occur. If a coronary artery is blocked completely, a heart attack results. Decreased blood flow to your brain can cause a stroke.

The higher your cholesterol levels, the greater your risk of heart disease and stroke. Given that heart disease is a top killer of men and women, this isn't a risk that you should ignore. However, eating in a heart-healthy way, being physically active and losing weight are things everyone can do to lower their cholesterol levels and their risks.

What's being measured when your cholesterol is checked? Why should some cholesterol referred to as "good," putting people at lower risk for heart disease, and another "bad"?

Types of cholesterol:
Your doctor may order tests to check your blood levels of cholesterol. Since cholesterol can't dissolve in the blood (it's not water-soluble), it doesn't circulate by itself. Instead, cholesterol travels through the bloodstream linked to "carriers" called lipoproteins.

There are three different types of lipoproteins. The two that are most important to remember in terms of your possible risk of heart disease are high-density lipoproteins (HDL) and low-density lipoproteins (LDL).

Cholesterol that is carried on low-density lipoproteins is called LDL cholesterol, the "bad" cholesterol. Higher levels of LDL cholesterol are associated with an increased risk for heart disease.

Cholesterol molecules that are linked to high-density lipoproteins are called HDL cholesterol, the "good" cholesterol. If you have higher levels of HDL cholesterol, you're at lower risk for heart disease.
Can't remember which cholesterol is "bad" and which is "good?"
Try this as a way to remind yourself: LDL cholesterol ("bad") is "low-down." HDL cholesterol ("good") comes "highly recommended."

"Good" and "bad" cholesterol:
Why should one type of cholesterol be labelled "good," putting people at lower risk for heart disease, and another labelled "bad?" Because LDL is the main carrier of cholesterol to body tissues, and HDL carries cholesterol away from body tissues.

When you have a lot of LDL cholesterol, there is a greater danger that too much may be deposited in artery walls, which may then become damaged. The arteries may develop a cholesterol and fatty build-up called a plaque on the inside, referred to as atherosclerosis, or "hardening of the arteries."

Cholesterol build-up can prevent adequate amounts of blood from flowing to the heart and may lead to complete blockage of an artery. It is the most common cause of CHD, and happens so slowly that you are not even aware of it. The higher your LDL cholesterol, the greater your chance of this build-up.

When you have higher levels of HDL in your blood, it means that more high-density lipoproteins carry cholesterol away from arterial walls and to the liver. The liver then eliminates the cholesterol from the body by excreting it in the bile. Clearly, the more this happens, the less likely is cholesterol to accumulate in arterial walls and worsen the progression of atherosclerosis.