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Your blood offers many clues about your heart health.

When the heart muscle is damaged due to a blocked artery, certain cardiac or heart enzymes slowly leak into the blood. Measuring their presence is one of the best ways to confirm a heart attack has occurred.

Importance of Blood Tests

A blood test coupled with other important tests can provide additional information that can guide treatment and determine the long-term outcome in someone who has suffered a heart attack.

The first blood sample is usually taken in the emergency room. Additional blood samples are obtained every six to eight hours for the first 24 hours after hospital admission.

Types of Blood Tests


The presence of troponin is the most accurate indicator that a heart attack has occurred because it is a heart-specific protein. When a piece of heart muscle dies, the cell breaks open and releases its contents in the bloodstream, including troponin.

Even slight elevations in troponin levels can indicate some heart damage. However, fluctuations in troponin levels as diagnosed in a series of blood tests done over several hours is a tell-tale sign that the patient has had a heart attack or some other damage to the heart.

Troponin levels can still be positive for several days in patients who experience heart-related chest pain, discomfort, or other symptoms who do not immediately seek medical attention.

Learn more about cardiovascular testsLearn More About Cardiovascular Tests


The thyroid is a butterfly shaped gland found at the base of the throat below the Adam’s apple. It controls how the body uses energy, makes proteins, and interacts with other hormones. Fluctuations in the thyroid can precipitate heart problems.

An overactive thyroid makes your heart go faster and can cause a different form of heart beat. Including sinus tachycardia or atrial fibrillation.

Sinus tachycardia is a heart rate of 100 beats per minute or more. The normal heart rate in the average adult ranges from 60 to 100 beats per minute. Atrial fibrillation is a rapid, irregular heartbeat, which can lead to heart problems and possibly stroke.

Undiagnosed hypothyroidism (when the thyroid doesn’t produce enough hormones) can cause elevated levels of “bad” cholesterol. If left untreated, a fatty substance can build in the walls of your arteries and harden – a process known as atherosclerosis. Atherosclerosis causes the arteries to narrow and slows down or blocks blood fl ow to the heart. When this happens, you may experience chest pain. A heart attack occurs when the blood supply to a portion of the heart is completely cut off.

C-reactive Protein

C-reactive protein (CRP) is a protein in the liver that is produced as part of your body’s response to injury or infection.

The presence of C-reactive protein is a signal that there is inflammation in the body. That frequently inflammation is related to high cholesterol and can be a blood marker for coronary artery disease.

According to the American Heart Association, your CRP test 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)

Inflammation plays a central role in atherosclerosis. Measuring CRP alone won’t tell your doctor you have heart disease. But factoring CRP test results with other blood tests and risk factors for heart disease helps create an overall picture of your heart health.

Hemoglobin A1c

Hemoglobin A1c is a blood test that indicates the average amount of sugar in your blood over a three-month period. Hemoglobin is a substance within red blood cells that carries oxygen throughout your body. When your blood sugar is too high, sugar builds up in your blood and combines with your hemoglobin, becoming “glycated.”

tube of blood

Cardiologists use Hemoglobin A1c levels to gauge how well-controlled someone’s diabetes is. If someone has poorly controlled diabetes, then his or her risk for heart attack may be higher because it can create a bad metabolic environment for the heart vessels and makes the fatty cholesterol plaque buildup aggressively.

The higher the percentage of hemoglobin A1c in the blood, the higher the risks of developing complications related to diabetes.

Research also indicates that some long-term damage (especially to the heart and circulatory system) mafy already be occurring in patients who have pre-diabetes.

Quick Facts About Hemoglobin A1c

  • The normal range for the hemoglobin A1c test for people without diabetes is between 4 - 5.6%.
  • An increased risk of diabetes is indicated between 5.7% - 6.4% while diabetes is indicated at hemoglobin A1c levels of 6.5 percent or more.
  • Patients with diabetes should be tested every three months to determine whether their blood sugars are below 7 percent or at least within the target level of control.

Experts recommend that people who have their diabetes in check should get the blood test at least twice a year.