Which blood tests do you really need? And how often should you get them done?

Which blood tests do you really need? And how often should you get them done?

By Laura Entis

detail of hand in blue nitrile glove holding vile of bloodPhoto: Shutterstock
Sometimes it may feel like almost every visit to the doctor includes a dreaded blood draw. Blood tests can reveal a lot about the state of your health. But whether you should get a specific test (and how often) depends on your health and medical history; more is not always better.

Here’s what to know about three blood tests everyone should get and three others you may want to consider.

Complete Blood Count
A complete blood count (CBC) measures red and white blood cells as well as platelets. It can help identify infections, conditions like anemia, and even blood cancer.
The test “also looks at kidney and liver function, thyroid function, and electrolytes such as potassium, sodium, and calcium,” says Stephen Kopecky, MD, a cardiologist at the Mayo Clinic in Rochester, Minn.

How often should you get one? It depends. If you’re in good health, “every two to three years is fine,” Kopecky says. But if you have a condition such as kidney disease that needs to be monitored more closely or if you’re on certain medications, including some prescription drugs for high blood pressure or cholesterol, “it should be done annually.”

Metabolic Panel
A basic metabolic panel is used to assess glucose levels and can screen for diabetes and prediabetes, as well as lung and kidney function. A comprehensive panel includes all of the above plus six different tests of liver function. Both measure electrolytes and typically require fasting.

How often should you get one? The U.S. Preventive Services Task Force recommends every three years for adults who are obese or overweight but have normal glucose levels. Some other experts recommend that schedule for everyone 45 and older.

Lipid Panel
A lipid panel, which may require fasting beforehand, measures cholesterol and triglyceride levels. High or borderline high results can indicate an increased risk of heart disease.

How often should you get one? Every year for those over 65, according to the National Institutes of Health.

A1C
An A1C test measures your average blood sugar levels over the past three months and can be a useful tool for diagnosing diabetes and prediabetes. It doesn’t require fasting, Kopecky says. But it’s often not covered by Medicare, says Matthew Weissman, MD, site chair of the department of medicine at Mount Sinai Beth Israel Hospital and Mount Sinai Downtown.

Who should get one? The Centers for Disease Control and Prevention recommends everyone over 45 get at least a baseline A1C. If your result is normal but you have risk factors such as being overweight, the agency advises repeating the test every three years.

TSH
A TSH (thyroid-stimulating hormone) test can flag dysfunction of the thyroid gland, either overactivity (hyperthyroidism) or underactivity (hypothyroidism), says C. Noel Bairey Merz, MD, director of the Barbra Streisand Women’s Heart Center at Cedars-Sinai in Los Angeles. While treatable and rarely life-threatening, a thyroid imbalance “affects pretty much every organ system,” Bairey Merz says, which can lead to a wide range of symptoms, including weight changes and sleep problems.

Who should get one? If you have a family history of thyroid disease, Weissman recommends getting tested every few years. If you don’t and you’re asymptomatic, the evidence on regular screening is insufficient. “For many aging adults, it is a reasonable screening test,” Bairey Merz says.

Vitamin D
Testing for vitamin D is somewhat controversial. Proponents, including Kopecky, say it can be useful for flagging a common deficiency. Critics, Bairey Merz included, point to randomized trials that have raised questions about the health benefits of taking vitamin D supplements.

Who should get one? In Weissman’s practice, he generally recommends the test only for those with osteoporosis to ensure vitamin D deficiency isn’t a potential cause. “There has been mixed data around what diseases supplementing vitamin D can actually help,” he says.

Editor’s Note: This article also appeared in the February 2024 issue of Consumer Reports On Health.