Several blood tests can detect heart problems, ranging from emergency markers that reveal an active heart attack to routine screenings that estimate your long-term risk of heart disease. The right test depends on whether you’re in an emergency room with chest pain or sitting in your doctor’s office for a checkup. Here’s what each test measures and what the results mean.
Troponin: The Primary Heart Attack Test
Troponin is the single most important blood test for detecting heart damage. It measures a protein that heart muscle cells release when they’re injured or dying. Under the 2025 ACC/AHA guidelines, troponin (specifically high-sensitivity troponin) is the preferred biomarker for diagnosing a heart attack. A level above the 99th percentile upper reference limit for the specific test being used signals myocardial injury.
What makes troponin especially useful in an emergency is the pattern over time. A heart attack produces a characteristic rise and fall in troponin levels across serial blood draws. If you arrive at the ER with chest pain and your symptoms started more than two hours ago, a single high-sensitivity troponin reading below the detection limit can help rule out a heart attack quickly. For most patients, hospitals draw troponin at arrival and again one to two hours later. If both readings are very low, that’s strong evidence against an active heart attack.
Older markers like CK-MB and myoglobin were once standard but have largely been replaced. Myoglobin rises faster (useful within 3 to 6 hours of symptoms), but troponin is far more specific to the heart. CK-MB reaches its best diagnostic accuracy around 7 hours after symptoms begin, while troponin’s reliability improves over 12 hours, making it ideal for detecting damage that other markers might miss.
BNP and NT-proBNP: Heart Failure Markers
These tests measure hormones your heart releases when it’s under strain, particularly when the chambers are stretched from fluid overload. They’re the go-to blood tests for diagnosing and monitoring heart failure.
Normal BNP is generally below 100 picograms per milliliter (pg/mL). For NT-proBNP, normal depends on your age: under 125 pg/mL if you’re younger than 75, and under 450 pg/mL if you’re older. BNP levels above 100 or NT-proBNP levels above 900 pg/mL may indicate heart failure. One important caveat: obesity can lower BNP levels, which means the test might underestimate heart failure in people carrying extra weight. Your doctor interprets these numbers alongside your symptoms, not in isolation.
Lipid Panel: Your Long-Term Risk Profile
A lipid panel measures cholesterol and triglycerides in your blood. It’s the most common screening test for cardiovascular risk and typically requires 8 to 12 hours of fasting beforehand. The panel reports four key numbers: total cholesterol, LDL (“bad”) cholesterol, HDL (“good”) cholesterol, and triglycerides.
Target levels vary based on your overall risk. For most adults at moderate risk, the goal is LDL below 100 mg/dL. If you’re at high risk (a 10% or greater chance of a cardiovascular event in the next 10 years), guidelines recommend getting LDL below 70 mg/dL. For people who already have heart disease and are at very high risk of another event, the target drops further to below 55 mg/dL. Triglycerides at or above 150 mg/dL in someone with existing heart disease warrant closer attention and more aggressive cholesterol-lowering treatment.
High-Sensitivity CRP: Inflammation and Risk
High-sensitivity C-reactive protein (hs-CRP) measures inflammation throughout your body. Chronic, low-grade inflammation plays a major role in the buildup of plaque inside arteries, so this test helps estimate cardiovascular risk even when cholesterol levels look normal.
Results fall into three categories, measured in milligrams per liter. Below 1 is low risk. Between 1 and 3 is intermediate risk. At 3 or above, you’re in the high-risk category. This test is most useful for people whose risk isn’t obvious from standard factors alone. It’s not a diagnostic test for a specific condition; rather, it adds a piece to the overall picture.
D-Dimer: Ruling Out Blood Clots
A D-dimer test detects fragments left behind when blood clots break down. It’s primarily used to rule out dangerous clots like deep vein thrombosis (a clot in a leg vein) and pulmonary embolism (a clot in the lungs), both of which can severely strain or damage the heart.
The test works best as a “rule-out” tool. A low or normal D-dimer level means you probably don’t have a significant clotting problem. A high level doesn’t confirm a clot on its own, since inflammation, infection, surgery, and even pregnancy can elevate it. But it tells your care team whether imaging tests are needed to look further.
Lipoprotein(a): A Genetic Risk Factor
Lipoprotein(a), often written as Lp(a), is a type of cholesterol particle largely determined by your genetics. Unlike LDL, which responds to diet and medication, Lp(a) levels are mostly set at birth. A level at or above 50 mg/dL (roughly 125 nmol/L) is considered elevated across most major guidelines and signals increased risk of atherosclerotic heart disease.
Because Lp(a) doesn’t change much over your lifetime, most guidelines recommend measuring it just once. Testing is particularly valuable if you have a family history of early heart disease, if you’ve had a heart attack or stroke at a young age, or if your LDL cholesterol is very high (190 mg/dL or above). Knowing your Lp(a) level helps you and your doctor decide how aggressively to manage other risk factors you can control.
Electrolytes: Potassium and Magnesium
Your heart’s electrical system depends on a precise balance of minerals in your blood, especially potassium and magnesium. These are typically measured as part of a basic metabolic panel, which may require fasting.
For heart health, optimal serum potassium falls between 3.5 and 4.5 mEq/L. Levels outside that range, whether too high or too low, increase the risk of dangerous heart rhythm disturbances. Magnesium levels between 2.0 and 2.2 mg/dL are associated with the best outcomes in cardiac patients, with levels at 2.4 mg/dL or above linked to higher risk. These aren’t tests you’d request on your own, but they’re routinely checked during hospital stays, before surgery, and when you’re on medications (like diuretics) that affect mineral balance.
Which Tests You’ll Actually Get
The tests ordered for you depend entirely on the situation. In an emergency with chest pain or shortness of breath, expect troponin draws, a basic metabolic panel, and possibly BNP and D-dimer. For a routine checkup focused on prevention, a lipid panel is standard, and your doctor may add hs-CRP or Lp(a) if your family history or other risk factors raise concern.
Most of these tests use a simple blood draw from a vein in your arm. Results for troponin and BNP typically come back within an hour in an emergency setting. Lipid panels and other screening tests usually return within a day or two. If you’re scheduled for a lipid panel or metabolic panel, plan to fast for 8 to 12 hours beforehand. Troponin, BNP, D-dimer, hs-CRP, and Lp(a) do not require fasting.