6 Important Blood Tests You May Need for Your Overall Health

While no one loves to get their blood drawn, these tests can reveal much about our health, providing information on everything from cholesterol levels to kidney function. How often you should get blood tests depends on your age, health and the type of blood test but if you haven't had one in a while, you should ask your doctor if it's time for you to get it done. 

With all the different types of blood tests out there, it can be confusing to figure out which you need and when. To help, we spoke with doctors for their expert insights about some important blood tests you may want to talk to your doctor about. 

1. Complete blood count

The complete blood count routine test provides a snapshot of your body's blood production and immunity. The test measures a variety of components in your blood, including red blood cells, white blood cells and platelets.

Dr. Soma Mandal, a board-certified internist at Summit Health in New Providence, New Jersey, says that getting a CBC test is "recommended for individuals of all ages as part of a routine health examination or when symptoms suggest a potential health issue."

Dr. Maria Knöbel, medical director of Medical Cert UK, agrees that this foundational test is appropriate for many patients. She says the test is ideal for anyone undergoing a routine health check-up. Still, she advises that you may want to get it if you're "experiencing symptoms like persistent fatigue, unexplained bruising or frequent infections."

A CBC blood test can indicate lots of things, including:

• Allergies
• Anemia
• Certain cancers
• Heart disease
• Immune system disorders
• Infection
  
• Inflammation
• Iron deficiency
• Leukemia
• Low platelets (can affect blood clotting)
• Risk of clotting and bleeding
• Vitamin deficiency

Mandal explains that each lab may have slight variations for what they consider "normal" test results. The ranges typically accepted as normal for adults are:

Red blood cells: 4.5-5.9 million cells per microliter (men), 4.1-5.1 million cells per microliter (women)

White blood cells: 4,500-11,000 cells per microliter

Hemoglobin: 13.8-17.2 grams per deciliter (men), 12.1-15.1 grams per deciliter (women)

Hematocrit: 40.7%-50.3% (men), 36.1%-44.3% (women)

Platelets: 150,000-450,000 platelets per microliter

2. Lipid panel

Lipids are fats and fatty substances in your blood. One type of lipid is cholesterol, which is used as a source of energy. Too much "bad" cholesterol (low-density lipoprotein or LDL) can damage your heart.

You may need to get this test if you have cardiovascular disease or other risk factors. Mandal states this test is essential for anyone "at risk of cardiovascular diseases, including those with a family history of heart disease, smokers, people with hypertension or those who are overweight."

Knöbel explains that a lipid panel measures total cholesterol and also breaks it down into HDL/LDL:

• Triglycerides
• LDL (bad cholesterol)
• HDL (good cholesterol)
  

She says, "Elevated LDL levels are associated with an increased risk of heart disease, while high HDL levels are generally protective. Elevated triglycerides can also indicate a risk for heart disease and may be associated with other conditions like diabetes."

The normal parameters for a lipid panel in adults are:

Total cholesterol: Less than 200 mg/dL

LDL cholesterol: Less than 100 mg/dL

HDL cholesterol: 40 mg/dL or higher (men), 50 mg/dL or higher (women)

Triglycerides: Less than 150 mg/dL

3. Basic metabolic panel

The basic metabolic panel (BMP) measures what Knöbel calls "critical aspects of your body's chemistry." This includes glucose, calcium and electrolytes such as sodium, potassium and bicarbonate. The test also looks for kidney function indicators, such as blood urea nitrogen and creatinine.

"Glucose levels provide insight into blood sugar control," Knöbel explains. "Electrolyte imbalances can reveal issues related to dehydration, kidney disease or metabolic imbalances. Abnormal calcium levels can indicate issues with bone health or parathyroid function." BMP is often part of a routine exam. It also may be recommended for patients with diabetes or kidney disease or those at risk for these conditions.

The results of your BMP could indicate:

• Dehydration
• Deteriorating bone health
• Diabetes
• Hypertension
• Kidney disease

For adults, Mandal says the normal ranges for results of this test are:

Bicarbonate: 23-30 mEq/L

Blood urea nitrogen (BUN): 7-20 mg/dL

Calcium: 8.5-10.2 mg/dL

Chloride: 96-106 mEq/L

Creatinine: 0.6-1.3 mg/dL

Glucose: 70-99 mg/dL (fasting)

Potassium: 3.5-5.0 mEq/L

Sodium: 135-145 mEq/L

4. Hemoglobin A1C

The Hemoglobin A1C test, also called the HbA1c, is a blood test that measures your average blood sugar level over the past 2-3 months. Mandel explains that it's primarily used to diagnose and monitor diabetes and pre-diabetes. If you're overweight, have symptoms of diabetes, have a family history of diabetes or are over the age of 45, the doctor says you may also want to get this test. A daily sugar test gives you a short-term view of your blood sugar level. On the other hand, this test is a long-term view of how well your body is managing glucose.

Getting an HbA1c test could reveal a few things about your health:

• Diabetes
• Poor blood sugar control (higher risk of diabetes-related complications)
• Pre-diabetes

Normal ranges for test results are:

Normal: Less than 5.7%

Pre-diabetes: 5.7% to 6.4%

Diabetes: 6.5% or higher

5. Thyroid function tests

If you are experiencing fatigue, weight changes, irregular heartbeat, hair loss or mood swings, you may want to get a thyroid function test. Typically prescribed only if you display symptoms such as those previously mentioned, this test measures the amount of thyroid-stimulating hormone in your blood. Your doctors can use the results to see how well your thyroid (a small, hormone-releasing gland in the front of your throat) is functioning. Mandal tells us this test is commonly included in routine health screenings, especially in women older than 60.

Your blood test may indicate:

• High TSH levels/hypothyroidism (an underactive thyroid)
• Low TSH levels/hyperthyroidism (an overactive thyroid)
  
• Abnormal levels of T3 and T4 (other thyroid disorders)
  

Doctors typically consider the following normal ranges for test results in adults:

TSH levels: 0.4-4.0 mIU/L

Free T4 levels: 0.8-1.8 ng/dL

Free T3 levels: 2.3-4.2 pg/mL

6. 25-hydroxy vitamin D

According to Mount Sinai, a hospital system in New York, some older patients can benefit from getting a 25-hydroxy test to check their vitamin D levels. People who are older than 65, have osteoporosis, get limited sun exposure and/or have celiac disease, Crohn's disease or ulcerative colitis may benefit from the test.

Most people get ample vitamin D from the sun. Both skin production and gut absorption of the vitamin declines as we age. It's important to find out if you don't have enough vitamin D because it helps with everything from bone health to immunity and energy levels.

The 25-hydroxy vitamin D will reveal two things:

• 25 hydroxy vitamin D3 (cholecalciferol)
• 25 hydroxy vitamin D2 (ergocalciferol)
  

There is some disagreement among doctors about what a healthy range is for vitamin D but one generally accepted range is 20 and 40 ng/mL.

Blood test FAQs

Why are blood tests important?

Blood tests are important because they can help doctors monitor your health and the effectiveness of treatments. They can also help doctors diagnose different medical conditions and determine the best treatment path. 

If my blood tests are normal, could I still have cancer?

Routine blood tests may not be able to detect most types of cancer so even if your blood tests come back normal, you could still have cancer. Cancers also require additional diagnostic and laboratory testing for confirmation. If you're concerned about a certain type of cancer, discuss this with your doctor. 

Which blood tests need to be fasting?

According to Harvard Health, fasting is often advised before tests such as glucose (blood sugar) and triglycerides, the latter of which is part of the cholesterol or lipid panel. Consult your doctor if you're confused about how long you should fast before your blood tests.

The bottom line

It's always important to discuss your health and any related concerns with your doctor before requesting any type of test. Based on your personal situation and health plan, your doctor may request blood work not on this list or say that you don't need some of the above tests.

As a general rule, many people can benefit from CBC, lipid panel, BMP and hemoglobin A1C even without any symptoms. Also, thyroid function and vitamin D tests should be considered if you experience any symptoms. If you're older, you may also want to talk to your physician about your vitamin D absorption.

If your labs are abnormal, you may need additional screening and more frequent repeat labs. If your labs are normal, these labs may only need to be repeated once a year while doing your annual exam with your primary doctor.