Before You Buy Function Health: A Physician’s Perspective

Estimated read time: ~7 min

Summary:

• Many labs in large panels are already part of routine preventive care, but only a small number of additional tests have evidence to support screening in healthy, asymptomatic adults.
• Broad, untargeted testing can cause harm through false positives, unnecessary follow‑up, anxiety, and care cascades—without improving long‑term health outcomes.
• Effective prevention is about precision, not volume: ordering the right tests for the right person at the right time, guided by evidence and clinical context.

In recent years, direct to consumer lab panels like Function Health have become increasingly popular. Some promise to measure everything from heart health and hormones to inflammation, nutrients, and even “biological age.” For many people, the appeal is obvious: if knowledge is power, then more data must mean better prevention.

But there is a really important principle in medicine that DTC lab companies will not admit—more information is not always better information—especially when you feel well. And recently I’ve found myself having to explain this to patients who bring their Function Health lab panels into clinic looking for explanations.

As a physician focused on prevention and long‑term health, I’m often asked whether large lab panels are helpful for people without symptoms. The answer is nuanced. Some tests are foundational to preventive care. Others can be useful in specific situations. And many, when ordered broadly in healthy adults, add noise rather than clarity. Understanding the difference can help you make smarter, calmer decisions about your health.

Preventive medicine is not about finding every possible abnormality. It’s about identifying conditions early when intervention clearly improves outcomes—before symptoms appear.

That’s why national guidelines exist. Organizations like the US Preventive Services Task Force (USPSTF), the American College of Cardiology (ACC), and the American Heart Association (AHA) regularly review evidence to determine which tests actually reduce illness, disability, or death when used for screening in people who feel well.¹–³

These recommendations are not about rationing care. They’re about avoiding harm from unnecessary testing, false positives, and downstream procedures that don’t improve health.

A large portion of what appears on Function Health’s lab panel actually overlaps with standard preventive care. It’s just disguised in fancy medical jargon to make you think it’s something greater than it is.

For most adults, routine screening already includes:

• Cholesterol testing to assess cardiovascular risk¹,²
• Blood glucose or hemoglobin A1c to screen for diabetes in appropriate age and risk groups⁷
• Complete blood count (CBC) to evaluate anemia and blood disorders⁴
• Comprehensive metabolic panel (CMP) to assess kidney, liver, and electrolyte function⁴
• Thyroid‑stimulating hormone (TSH) as part of cardiovascular risk evaluation⁴
• Urinalysis and urine albumin to screen for kidney disease⁴

Note that Function Health will have a long list of individual tests underneath a health category, but many of these tests are actually included in one of the routine panels above you’re probably already getting at your doctor’s office. For example, a complete blood count (CBC) with differential includes hematocrit, hemoglobin, MCH, MCHC, MCV, MPV, platelet count, RBC count, and red cell distribution width. While Function Health lists them out to make it seem like they’re 9 different tests, in actual practice it’s all lumped into one “CBC”. They do this with many of their tests.

These tests form the backbone of preventive care in the United States. They are evidence‑based, widely recommended, and genuinely useful for identifying common, treatable conditions early.

Newer screening biomarkers are re-evaluated by professional societies. For example, recently the American Heart Association recommended one-time screening for lipoprotein(a), or Lp(a) in all individuals. This is a genetically determined cholesterol particle associated with increased cardiovascular risk.⁹–¹¹

When counted individually, roughly half of the tests in many large panels like Function Health fall into this category. That’s reassuring—and important to acknowledge. The remaining tests fall into a grey-area spectrum. Some are more useful than others, but most are not supported by evidence. We’ll cover those tests now.

Beyond routine labs, a small number of additional tests have enough evidence supporting their use, at least in specific populations, even when symptoms are absent.

ApoB reflects the number of atherogenic particles in the blood and can be helpful in people with diabetes, kidney disease, or elevated triglycerides—situations where standard LDL cholesterol may underestimate risk.⁹ ApoB is emerging as a more accurate indicator of atherogenic (‘bad cholesterol’) risk than LDL. In some cases, the two markers don’t align, and when they diverge, ApoB tends to better predict cardiovascular outcomes. That’s why I prioritize tracking ApoB over LDL.

hs‑CRP measures inflammation and has been shown to predict cardiovascular events, even in people without traditional risk factors.¹⁴–¹⁷ However, guideline recommendations differ. The ACC supports broader use, while the USPSTF has concluded that evidence is still insufficient to recommend routine screening.³ I prioritize tracking hs‑CRP because it plays a direct role in disease processes—and, importantly, it’s something we can actively address when it’s elevated.

PSA testing is supported for men aged 55 to 69 years through shared decision‑making, weighing potential benefits and harms.¹⁸,¹⁹ These tests are not “bad”, they’re just not perfect because they’re very prone to false positives. They’re simply context‑dependent. Used thoughtfully and longitudinally, such as with PSA velocity, it can add value in prostate cancer screening. Used indiscriminately, it often doesn’t.

Most remaining tests on expansive panels fall into this category.

These include:

• Advanced lipid subfractions (LDL particle size, pattern, peak size), which are not recommended for routine risk assessment by major cardiology guidelines⁹,²⁰–²². You can capture your cholesterol-contributing cardiovascular risk with just a lipid panel, ApoB, and Lp(a).
• Micronutrient panels (vitamin D, zinc, magnesium, omega‑3s), which lack evidence for routine screening in healthy adults²³–²⁷. Targeted, intentional assessments when clinically indicated are the best way to go about testing these.
• Autoimmune markers (ANA, rheumatoid factor), which are diagnostic tools—not screening tests⁸. These do not belong in general screening tests.
• Hormonal panels (testosterone, estrogen, DHEA, cortisol), which are indicated only when symptoms suggest a specific disorder. Hormones fluctuate constantly in healthy people. That’s why sending these tests only when the clinical context makes sense is the gold standard.
• Pancreatic enzymes, toxin screens, and “biological age” tests, none of which have guideline support for screening asymptomatic adults.

These tests are not useless—but they are misused when applied broadly without a clinical reason.

It’s intuitive to think that more data leads to better decisions. In reality, broad testing in healthy people often creates problems. The “noise” rather than “signal” that these large lab panels create are due to the following principles.

When dozens of tests are ordered at once, it becomes statistically likely that something will fall outside the reference range—even if nothing is wrong.⁸ This is because medical screening tests aren’t perfect. When physicians interpret blood tests they do not automatically believe the result, but interpret it the entire clinical context. For example, an ANA test used to screen for autoimmune disease has a false positive rate of 30-70%. Imagine how many people might be walking around thinking they have an autoimmune disorder when in reality it was just a false positive.

An abnormal result often leads to repeat testing, imaging, referrals, or procedures. Many of these cascades do not improve outcomes and can expose patients to unnecessary risk.²⁸,²⁹ More testing often just contributes to the “noise” that was first propagated by testing for something that should never have been tested for in the first place.

Unexpected abnormalities can create stress, label people as “sick,” and shift focus away from behaviors that actually improve health—like sleep, movement, nutrition, and stress management.

Large studies have shown that routine “general health checks” with extensive lab testing do not reduce mortality and often increase healthcare utilization without clear benefit.⁸

A helpful way to think about lab testing is the difference between a flashlight and a floodlight. Targeted testing uses a flashlight: it’s guided by age, sex, family history, symptoms, and risk factors. It asks, “What question are we trying to answer?” “What is the pre-test probability that a patient has this condition and how will the results of this blood test affect the post-test probability?” It’s intentional. Not random. And it has to be to avoid the above issues.

Shotgun testing uses a floodlight: it illuminates everything at once, regardless of relevance. This approach often finds incidental abnormalities that don’t change outcomes but may change lives for the worse. Prevention works best when it’s precise, not exhaustive.

If you’re considering a large lab panel, a few questions can help guide the decision:

• What specific decision will this test influence?
• What happens if the result is abnormal?
• Is this test recommended for someone like me, or only in certain situations?

These questions should be discussed with an un-biased physician that knows you and your medical history. Knowing the indications for lab tests is why doctors spend 7+ years in school and training. Good preventive care is not about avoiding testing—it’s about using the right tests at the right time for the right person. And shotgun testing like Function Health is the opposite of this.

Comprehensive lab panels can feel empowering, but more data does not automatically mean better health. Many core labs are already part of routine preventive care. A small number of additional tests can be helpful in certain individuals. And a large portion of commonly marketed tests are not recommended for screening and may cause more harm than benefit when used indiscriminately.

True healthspan medicine isn’t about measuring everything. It’s about measuring what matters—and knowing when not to measure at all.

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