Introduction

Your blood offers many clues about your heart health. For example, high levels of "bad" cholesterol in your blood can be a sign that you're at increased risk of having a heart attack. And other substances in your blood can help your doctor determine if you have heart failure or are at risk of developing plaques in your arteries (atherosclerosis).

It's important to remember that one blood test alone doesn't determine your risk of heart disease and that the most important risk factors for heart disease are smoking, high blood pressure, high cholesterol and diabetes.

Click on the tabs at the left to look at some blood tests you may have in your diagnosis, treatment and management of heart disease.

C-reactive protein

C-reactive protein (CRP) is a protein your liver produces as part of your body's response to injury or infection (inflammatory response).

CRP is a sign of inflammation somewhere in the body. However, CRP tests can't pinpoint where in the body this may be happening. Inflammation plays a central role in the process of atherosclerosis, in which fatty deposits clog your arteries. Measuring CRP alone won't tell your doctor your risk of heart disease. But factoring in CRP test results with other blood test results and risk factors for heart disease helps create an overall picture of your heart health.

According to the American Heart Association, your CRP test result can be interpreted as putting your heart disease risk at:

• Low risk (less than 1.0 milligrams per liter, or mg/L)
• Average risk (1.0 to 3.0 mg/L)
• High risk (above 3.0 mg/L)

The American Heart Association doesn't yet recommend CRP screening for the general public — only those at known risk of heart disease.

Cholesterol-lowering statin medications may reduce CRP levels and decrease your heart disease risk, but it's not recommended that you take statin medications solely to decrease your CRP level. Talk to your doctor if you're concerned about your CRP level.

Fibrinogen

Fibrinogen is a protein in your blood that helps blood clot. But too much fibrinogen can cause a clot to form in an artery, leading to a heart attack or stroke.

Having too much fibrinogen may also mean that you have atherosclerosis. It may also worsen existing injury to artery walls.

Your doctor may check your fibrinogen level if you have an increased risk of heart disease. Smoking, inactivity, drinking too much alcohol and taking supplemental estrogen — whether from birth control pills or hormone therapy — may increase your fibrinogen level.

A normal fibrinogen level is considered to be between 200 and 400 mg/L.

Homocysteine

Homocysteine is a substance your body uses to make protein and to build and maintain tissue. But too much homocysteine may increase your risk of stroke, certain types of heart disease, and disease of the blood vessels of the arms, legs and feet (peripheral artery disease).

Your doctor may check your homocysteine level if you've had cardiovascular problems but don't have any of the traditional risk factors, such as smoking. Your doctor may also suggest screening if any family members developed heart problems at a young age or have high homocysteine levels. A normal homocysteine level is between 4.4 and 10.8 micromoles per liter (µmol/L).

Your homocysteine level may drop if you get plenty of folate (folic acid) and B vitamins in your diet through foods such as green, leafy vegetables and fortified grain products or through supplements.

But it's not known if reducing your homocysteine level actually reduces your risk of death from heart disease.

Cholesterol test

A cholesterol test, also called a lipid panel or lipid profile, measures the fats (lipids) in your blood. The measurements can indicate your risk of having a heart attack or other heart disease. The test typically includes measurements of:

• Total cholesterol. This is a sum of your blood's cholesterol content. A high level can put you at increased risk of heart disease. Ideally, your total cholesterol should be below 200 milligrams per deciliter (mg/dL) or 5.2 millimoles per liter (mmol/L).
• Low-density lipoprotein (LDL) cholesterol. This is sometimes called the "bad" cholesterol. Too much of it in your blood causes the accumulation of fatty deposits (plaques) in your arteries (atherosclerosis), which reduces blood flow. These plaques sometimes rupture and lead to major heart and vascular problems. Ideally, your LDL cholesterol level should be less than 130 mg/dL (3.4 mmol/L).
• High-density lipoprotein (HDL) cholesterol. This is sometimes called the "good" cholesterol because it helps carry away LDL cholesterol, keeping arteries open and your blood flowing more freely. Ideally, your HDL cholesterol level should be 60 mg/dL (1.6 mmol/L) or higher, though it's common that HDL cholesterol is higher in women than men.
• Triglycerides. Triglycerides are another type of fat in the blood. High triglyceride levels usually mean you regularly eat more calories than you burn. High levels increase your risk of heart disease. Ideally, your triglyceride level should be less than 150 mg/dL (1.7 mmol/L). The American Heart Association (AHA) recommends that a triglyceride level of 100 mg/dL (1.1 mmol/L) or lower is considered "optimal." The AHA says this optimal level would improve your heart health.

Lipoprotein (a)

Lipoprotein (a), or Lp(a), is a type of LDL cholesterol. Your Lp(a) level is determined by your genes and isn't generally affected by lifestyle.

High levels of Lp(a) may be a sign of increased risk of heart disease, though it's not clear how much risk. Your doctor might order an Lp(a) test if you already have atherosclerosis or heart disease but appear to have otherwise normal cholesterol levels.

Lp(a) is often tested if you have a family history of early-onset heart disease or sudden death. It should also be tested if your LDL cholesterol doesn't respond well to drug treatment.

Natriuretic peptides

Brain natriuretic peptide, also called B-type natriuretic peptide (BNP), is a protein that your heart and blood vessels produce. BNP helps your body eliminate fluids, relaxes blood vessels and funnels sodium into your urine.

When your heart is damaged, your body secretes high levels of BNP into your bloodstream to try to ease the strain on your heart. BNP levels may also rise if you have new or increasing chest pain (unstable angina) or after a heart attack.

Your BNP level can help in the diagnosis and evaluation of heart failure and other heart conditions. Normal levels vary according to age and gender. One of the most important uses of BNP is to try to sort out whether shortness of breath is due to heart failure. For people who have heart failure, establishing a baseline BNP can be helpful and future tests can be used to help gauge how well your treatment works.

A variation of BNP called N-terminal BNP also is useful in diagnosing heart failure and in some laboratories is used instead of BNP. N-terminal BNP may also be useful in evaluating your risk of heart attack and other problems if you already have heart disease.

A high level of BNP alone isn't enough to diagnose a heart problem. Your doctor will also consider your risk factors and other blood test results.