Don’t be surprised if your doctor has a few changes in store for your routine blood work. Some tests might be added to or subtracted from your lab order this year, or your doctor might talk about interpreting the results a little differently. Here are several tests to discuss with your doctor.
A vitamin D test
Vitamin D is important for many aspects of health, including calcium absorption, healthy bones, inflammation reduction, and immune function. Doctors debate how much D we need, and most guidelines say we don’t have enough evidence to support routine screening in healthy people. Yet many doctors still regularly order the tests.
The test measures a type of vitamin D called 25-hydroxyvitamin-D. Until recently, levels considered healthy or “sufficient” varied widely, ranging from 12.5 nanograms per milliliter (ng/mL) to 60 ng/mL. Several guidelines recommend levels above 20 or 30 ng/mL.
What’s new: The Endocrine Society, one of the main organizations that steers vitamin D practices, published new vitamin D guidelines in the August 2024 issue of The Journal of Clinical Endocrinology and Metabolism.
In a major shift, the guidelines ditched the concepts of vitamin D “sufficiency” and “deficiency” and strongly recommended against routine vitamin D testing. The exception is for people with specific conditions like chronic kidney disease or difficulty absorbing vitamin D (such as Crohn’s disease). The recommendations are based on a lack of evidence for routine testing benefits.
The Endocrine Society guidelines also say that most healthy adults don’t need vitamin D supplements. Exceptions include pregnant women, people with prediabetes, and people ages 75 or older. These groups may benefit from low dose vitamin D supplementation (about 1,000 IU per day), but should also try to get the vitamin through fortified foods or incidental sun exposure.
What you should do: Talk to your doctor about the new guidelines. If you have a condition that causes vitamin D deficiency, fall into one of the above groups, or take a medication that can lower vitamin D levels, you might need periodic screenings.
“Otherwise, it’s unlikely that you need to be routinely tested or take a supplement. Most of us get enough D from foods like fish, fortified dairy products, and fortified cereals. And the body can make vitamin D in the skin from just 10 to 15 minutes of sun exposure a few times per week,” says Dr. JoAnn Manson, Harvard’s leading vitamin D researcher and chief of the Division of Preventive Medicine at Harvard-affiliated Brigham and Women’s Hospital. “If you’re concerned that you’re not getting enough vitamin D, it’s safe to take a supplement with 1,000 to 2,000 IU daily. But our large, randomized trials of vitamin D suggest that most people already get the vitamin D they need and supplements have limited benefits.”
Blood tests to detect heart disease
You’re probably familiar with a routine cholesterol test that measures various fats in the blood (such as “bad” LDL cholesterol) that can increase your risk of heart disease and stroke. This year, your doctor might also order two additional blood tests.
One measures lipoprotein(a), or Lp(a). If Lp(a) levels are very high, your risk of heart attack, stroke, and some heart valve problems can increase, even if standard cholesterol levels are normal. High Lp(a) is inherited, which means you only need to have it measured once, as currently recommended by the National Lipid Association. The test is covered by insurance, but few people get it, primarily because we didn’t have treatments to lower Lp(a) until recently.
The other test measures C-reactive protein (CRP), a substance the liver makes when there’s inflammation in the body. Results of the test, called a high-sensitivity C-reactive protein test (hsCRP), can indicate inflammation levels as well as heart attack or stroke risk. The test is usually covered by Medicare. It’s not always routinely ordered, but it is endorsed by the American Heart Association to help predict heart attack risk.
What’s new: A Harvard study published Aug. 31, 2024, in The New England Journal of Medicine suggested that LDL, hsCRP, and Lp(a) tests (considered together) might predict stroke and heart problems decades in advance.
The research involved about 28,000 women (average age 54), followed for up to 30 years, whose levels of LDL, CRP, and Lp(a) were measured at the start of the study. All three biomarkers were linked to heart attack and stroke risk, especially CRP. Risks increased even further for people who had high levels on two or even three of the different tests.
What you should do: “Everyone, regardless of gender, should have all three of these measured together, preferably in your 30s or 40s, since prevention needs to start early,” says Dr. Paul Ridker, the study’s lead author and director of the Center for Cardiovascular Disease Prevention at Harvard-affiliated Brigham and Women’s Hospital.
If your doctor hasn’t yet ordered these tests for you, ask about them. “As some of this information is new to primary care physicians, many patients are bringing the research paper with them to their office visits,” Dr. Ridker says. Beyond lifestyle changes, your doctor may recommend specific treatments based on your test results.
A complete blood count (CBC)
A CBC looks at components of blood that indicate if you have various conditions, such as anemia, infection, and blood cancers.
The routine test measures the amount and characteristics of red blood cells, five types of white blood cells, platelets, and hemoglobin (a protein in red blood cells that carries oxygen), and calculates such values as hematocrit (the percentage of blood made of red blood cells).
Results for each measurement are compared against a standardized “normal” range. For example, a red blood cell count between 4.0 and 5.4 million cells per microliter (mcL) is considered normal for women, and 4.5 to 6.1 million/mcL is normal for men. Ranges can vary slightly by lab. A result outside the normal range is considered abnormal.
What’s new: A Harvard study published online Dec. 11, 2024, by Nature suggests that it might be more useful to compare your latest CBC results to your previous numbers, rather than to standard reference points.
Scientists evaluated the CBCs of more than 12,000 healthy people who had five tests over 20 years. Participants’ results didn’t change much, regardless of where the numbers fell within the normal range. Each person had a unique combination of “set points.”
Researchers say changes in these set points might help doctors catch health problems earlier, which is important for conditions such as diabetes or heart disease. “Normal ranges are too broad and should be narrowed for each person. That interval might be lower for some people and higher for others,” says Dr. John Higgins, the study’s senior author and a pathologist at Harvard-affiliated Massachusetts General Hospital.
Another finding from the study: participants whose set points fell into the lower most or upper most end of a measurement’s normal range had higher rates of disease diagnosis and death within 10 years, compared with people whose set points stayed in the middle of the normal range.
What you should do: Keep an eye on your CBC results, learn what’s normal for you, and talk to your doctor if you see changes. Bring this article if you feel it will help. “Set points give you a personalized benchmark to detect slight deviations from your steady state and help us interpret other diagnostic test results for a more accurate picture of health,” Dr. Higgins says.
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