PERSONALIZED NUTRITION

What is functional medicine, and how does it use supplements?

What functional and integrative medicine mean, how practitioners use history and labs to choose supplements, and how to judge the evidence and the marketing yourself.

The short version

Functional medicine is an approach that looks for the drivers behind symptoms by taking a long history and looking at diet, sleep, stress, environment and often lab tests. The NIH notes the term is sometimes used much like integrative health.
Practitioners commonly pair food and lifestyle changes with supplements chosen for the person in front of them, rather than a standard list for everyone.
Research on the model itself is early: a large 2019 study found modest quality-of-life gains, but it was observational, so it cannot show cause and effect.
To judge a supplement, look for randomized controlled trials in people like you, using the dose and form you would actually take, measuring an outcome you care about.
Be wary of products that promise to fix a disease, claim FDA approval, hide amounts in blends, or lean on the idea that natural means safe.
A personalized formula is a tool, not a clinician. Apiece builds one daily blend from your goals and, optionally, your recent labs, and you should still share it with your own doctor.

What does functional medicine mean?

Functional medicine is a style of care that tries to find and address the underlying drivers of symptoms, with food and lifestyle as the first tools. There is no single legal definition, and practitioners range from medical doctors to nutrition professionals.

The NIH's National Center for Complementary and Integrative Health (NCCIH) separates a few related terms. A non-mainstream approach used together with conventional medicine is complementary; used in place of it, alternative. Integrative health brings conventional and complementary approaches together in a coordinated way. NCCIH notes that functional medicine sometimes refers to a concept similar to integrative health, while other times it describes something closer to naturopathy.

A functional medicine program studied at a large US academic health system describes the model as looking at how lifestyle, environment, genes and the microbiome interact, and at basic functions such as digestion, energy production and repair.

How do practitioners use labs and history to personalize supplements?

The short answer: they start with a detailed history, add lab results where useful, and then match supplements to specific gaps or goals, rechecking over time.

History: a timeline of symptoms, diet, sleep, stress, activity, digestion, medicines and family history.
Labs: common choices include a blood count, ferritin (iron stores), vitamin D, vitamin B12, blood sugar markers, lipids and thyroid tests.
Plan: food and habit changes first, with supplements to fill a specific need, such as iron when ferritin is low.
Follow-up: repeat labs and symptom check-ins to see whether anything changed.

Good practice here is not unique to functional medicine. Any clinician can and should ask what a test result will change about the plan. It is reasonable to ask the same question of any practitioner who suggests a large panel of specialty tests.

Does functional medicine work? What the research shows

Evidence on the model as a whole is limited and mostly observational. The best-known study, published in JAMA Network Open in 2019, compared 1,595 patients at a functional medicine center with patients at family health centers in the same health system.

At 6 months, functional medicine patients improved more on a standard physical health quality-of-life score: 1.59 points versus 0.33 points, in 398 matched pairs. At 12 months, the difference between groups was no longer significant in the main comparison. The authors called their results hypothesis generating and asked for prospective studies.

Because patients chose their care, and the program bundled diet, lifestyle coaching, longer visits and supplements, this kind of study cannot tell you which piece helped, or whether supplements helped at all. That is why each supplement still needs its own evidence.

How do you judge the evidence behind a supplement?

Ask four questions: what kind of study, at what dose and form, in which people, and measuring what? A product can cite real research and still not match any of the studies it points to.

Study type: randomized controlled trials (RCTs) compare people given the supplement with people given a placebo, so they can show cause and effect. Observational studies only show that two things travel together.
Size and quality: a 2021 review of magnesium for sleep in older adults found only 3 RCTs with 151 people. Sleep onset was about 17 minutes faster, but the evidence was rated low to very low quality.
Dose and form: in a 2022 analysis of 13 RCTs (1,126 people), CoQ10 reduced fatigue scores, and higher daily doses and longer use were linked to larger effects. A product with a token amount is not the same thing.
Population: a 2012 trial found iron reduced fatigue in menstruating women who were not anemic but had ferritin below 50 µg/L. It says little about people whose iron stores are already normal.
Outcome: a change in a lab number is not the same as feeling or functioning better. Check what was actually measured.

What are the red flags in supplement marketing?

The clearest warning signs are disease promises, claims of FDA approval and hidden amounts. Here is what to look for and why.

Promises to fix a specific disease. Under US law, a product marketed as a remedy for a specific disease is legally a drug, not a supplement. (Supplements may describe effects on the body's structure or function.)
"Approved by the FDA." The FDA does not have authority to approve dietary supplements before they are sold. Companies are responsible for safety and labeling.
"Natural, so it's safe." NCCIH notes that natural does not always mean safe; some plant products have caused serious harm.
Proprietary blends that list a total weight but not each ingredient's amount, so you cannot compare them with the studies.
Products sold mainly for weight loss, sexual enhancement or bodybuilding, which NCCIH says are the groups most likely to contain hidden drugs.
Words like "standardized", "verified" or "certified" on their own, which NCCIH notes do not by themselves ensure quality or consistency.

Label accuracy is a real issue. A 2023 JAMA study of 25 melatonin gummy products found 22 were inaccurately labeled, with measured melatonin ranging from 74% to 347% of the stated amount.

Why should your doctor see your full supplement list?

Supplements can change how medicines work, so the people prescribing your medicines need the complete list. The FDA gives examples: St. John's wort can make many medicines less effective, including birth control pills, and ginkgo taken with the blood thinner warfarin may raise bleeding risk.

The FDA suggests bringing a written list of every supplement and medicine, with doses and how often you take them, to each appointment. This matters most if you take prescription medicines, are pregnant or breastfeeding, or have a long-term health condition.

Where does a personalized supplement formula fit?

A personalized formula can apply some of the same ideas, matching ingredients to your goals and lab results, but it is not medical care and does not replace a clinician.

Apiece builds one daily blend from up to five goals, optional symptoms, health details and, if you have them, recent lab results (Apiece does not order labs). Every ingredient and amount is listed, with no proprietary blends, and our safety rules leave out ingredients that don't suit common medicines or conditions, such as vitamin K for people on warfarin.

Think of the list as something to take to your next appointment. Your doctor or pharmacist knows your full picture, and that conversation is where personalization works best.

Questions

Is functional medicine the same as integrative medicine?

They overlap but are not identical. The NIH's NCCIH defines integrative health as bringing conventional and complementary approaches together in a coordinated way, and notes that functional medicine sometimes refers to a similar concept, while other times it describes something closer to naturopathy. Ask any practitioner about their training and licensing.

Do functional medicine practitioners always recommend supplements?

Not always. The model puts food and lifestyle first, and supplements are usually added for a specific reason, such as low ferritin or low vitamin D on a lab test. A plan with a long list of products and no clear reason for each is worth questioning.

Are dietary supplements approved by the FDA?

No. The FDA does not have authority to approve dietary supplements before they are marketed. Manufacturers are responsible for making sure their products are safe and labeled correctly, and the FDA mainly acts after products are on the market.

How can I tell if a supplement study applies to me?

Check that it was a randomized controlled trial, that the people studied resemble you (age, sex, health status, starting nutrient levels), that the dose and form match the product, and that the outcome measured is one you care about. If any of these differ, the result may not carry over.

Can a personalized supplement replace seeing a doctor?

No. A personalized blend can match ingredients to your goals and labs, but it cannot examine you, order tests or manage a health condition. Keep seeing your own doctor, and share your supplement list, especially if you take medicines or are pregnant.

Sources

Build my formula More from the Journal

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This page is general information, not medical advice. Check with your doctor or pharmacist before starting a supplement, especially if you take medication, are pregnant or nursing, or have a health condition. Updated 2026-10-20.