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What Can Micronutrient Testing Tell You About Your Health?

Written by Dr. Michael Ruscio, DC on September 30, 2025

Written by Dr. Michael Ruscio, DC on September 30, 2025 — Reviewed by Hannah Wright

• About Micronutrients|
• Micronutrient Testing Can Be Misleading|
• Common Micronutrient Tests|

Micronutrient testing is having a moment. Scroll through social media and you’ll see people swearing by elaborate blood panels to explain fatigue, brain fog, or stubborn health issues. These tests promise clarity—and sometimes, they do deliver helpful insights.

Micronutrients are small but mighty—powering your energy, immunity, hormones, and brain every second. When they’re low, you might feel drained, foggy, or run down. Many turn to fancy blood tests for answers, but these panels often overpromise and underdeliver. 

This guide cuts through the hype, showing what micronutrients do, when testing matters, and why a nutrient-rich diet often beats chasing perfect lab numbers.

What Are Micronutrients? 

Micronutrients are the vitamins and minerals your body relies on for thousands of tiny chemical and electrical reactions happening in your cells every second. Micronutrients influence nearly every system in your body—from your immune defenses and hormone balance to your nervous system and gut health.

Whereas macronutrients—carbohydrates, proteins, fats, and water—provide the energy and building blocks your body needs in larger amounts, micronutrients are required in much smaller doses. But their impact is just as essential.

Some of the most important micronutrients include 1:

• Iron
• Vitamin A
• Iodine
• Zinc
• Vitamin D
• B vitamins like folate (vitamin B9) and vitamin B12
• Vitamin C
• Vitamin A
• Vitamin E
• Copper
• Selenium
• Potassium
• Calcium
• Sodium
• Magnesium

Even though the body needs only trace amounts of these nutrients, people can develop inadequacies (common) or deficiencies (less common). 

• Nutrient inadequacy occurs when intake is below recommended levels but not low enough to cause serious health problems. 
• Nutrient deficiency is more severe and can impair normal body functions.

Inadequacies in micronutrients may show up as fatigue, low mood, getting sick more often, or other health challenges 1. It’s no surprise, then, that many people turn to micronutrient testing in hopes of uncovering hidden causes of their symptoms.

Micronutrient Tests

Micronutrient tests are designed to measure your levels of vitamins, minerals, antioxidants, and other nutrients—most often through a simple blood draw. In some cases, providers may use urine or hair analysis, but blood testing is the norm.

Micronutrient tests are especially popular in functional medicine, where the goal is to uncover subtle nutrient gaps that could be fueling your symptoms. However, micronutrient testing is generally recommended only for people who are at a higher risk of deficiency—like bariatric surgery patients, pregnant people, elderly people, and those with specific medical conditions—rather than the general population.

Commonly checked micronutrients include 1:

• Iron
• Vitamin A
• Zinc
• Iodine
• Folate (vitamin B9)
• Vitamin D
• Vitamin B12

These blood tests are often a smart starting point when you or your doctor suspect a nutrient deficiency, but they probably won’t be very helpful if you’re dealing with nutrient inadequacies.

Other panels, like broad organic acid tests, are far more expensive and less consistent in accuracy. They may promise a deep dive into your nutrient status, but they often provide more complexity (read: confusion) than clarity.

3 Reasons Micronutrient Testing May Be Misleading

Micronutrients are vital for health, but unless you have clear signs of a deficiency, testing them one by one rarely gives the clear answers people want. Many patients (and even doctors) expect these tests to pinpoint the cause of symptoms, only to be left with results that raise more questions than solutions.

Here are four key reasons micronutrient testing often misses the diagnostic mark for most people.

Reason #1: Blood Levels Don’t Show What Cells Actually Use

Blood tests measure what’s circulating—not what your cells are actually absorbing or using. That means results can look reassuring when problems exist, or alarming when there’s no real issue.

Take zinc, for example. A zinc blood test may not be the most reliable marker unless a severe deficiency is present, so clinicians will look for signs and symptoms of zinc deficiency to confirm the blood test results 2. In many cases, it’s more practical to focus on a nutrient-dense diet or add supplements based on your symptoms, monitor your improvements, and if necessary, examine your diet and gut issues (which might be blocking absorption).

Reason #2: Symptoms Speak Louder Than Lab Numbers

A skilled practitioner can often spot nutrient inadequacies from symptoms alone. For example, fatigue, nausea, appetite loss, and weakness are strong indicators of low magnesium. In these cases, adjusting the diet, adding a supplement, and tracking symptom improvement can be more efficient and effective than ordering a micronutrient panel.

Reason #3: “Normal Ranges” Don’t Fit Everyone

Micronutrient needs vary widely by age, sex, health status, and even stress or environmental exposure. Lab ranges are standardized for the “average” person, but what’s normal for a 22-year-old male athlete is very different from a pregnant woman or an older adult.

This is why patients sometimes fall within “normal” ranges yet still experience symptoms of a nutrient inadequacy. In these situations, evaluating symptoms and risk factors is often more useful than relying on labs alone.

Evaluating Common Micronutrient Tests

Doctors use different blood tests to check levels of key vitamins and minerals when signs of deficiency are present, but no single test tells the whole story. Here’s a look at the most common nutrients people get tested for, how the tests work, and which foods can help keep levels up.

Iron

Iron is vital for carrying oxygen in the blood and muscles, supporting energy use, growth, brain development, cell function, and hormone production. Common symptoms of iron deficiency anemia are: gut disturbances, weakness, fatigue, and difficulty concentrating 3. 

Iron deficiency is diagnosed using blood tests, but no single test is perfect. Hemoglobin and hematocrit are the most common tests for iron, though they aren’t very accurate on their own. Serum ferritin is a better test since it reflects iron stores and can detect low iron before anemia develops, but it may be misleading if inflammation is present 3. 

Because of this, doctors often combine tests and consider diet, supplements, and symptoms. Iron deficiency typically progresses in stages—starting with low iron stores, then reduced red blood cell production, and finally iron deficiency anemia 3.

Aside from iron-fortified breakfast cereals, good whole-food sources of iron include oysters, white beans, beef liver, lentils, spinach, and tofu 3. 

Vitamin A

Vitamin A is essential for overall health. It supports the immune system, cell growth, and organ development, including the heart, lungs, and eyes. It’s also crucial for reproduction and vision, helping the eyes detect light and maintain healthy corneas and eye tissues 4.

Signs or symptoms of vitamin A deficiency may include: night blindness that can lead to permanent blindness, anemia, lung diseases, and more frequent infections 4.

Plasma or serum retinol levels can indicate vitamin A deficiency: ≤20 mcg/dL suggests moderate deficiency, and ≤10 mcg/dL indicates severe deficiency 4. 

Some of the best food sources of vitamin A are beef liver, sweet potato (with skin), spinach, carrots, herring, cantaloupe, and ricotta cheese 4.

Zinc

Zinc is a vital mineral that supports the immune system, helps the body make DNA and proteins, aids growth and development, promotes wound healing, and is important for tasting food properly 5. 

Signs of deficiency in adults may include slow wound healing, impaired taste and smell, reproductive problems, premature birth, and cognitive or mental health problems 6.

Serum or plasma zinc is commonly measured to check zinc status, with normal levels around 80–120  mcg/dL. Levels below 70 mcg/dL in women or 74  mcg/dL in men suggest low zinc. Zinc measurements can be influenced by your age, your sex, the time of day, your diet, any illness, and your hormones, so doctors also consider risk factors and physical signs when evaluating zinc status 6.

Most people can get enough dietary zinc by regularly eating oysters, meat, fish, poultry, shellfish, beans, nuts, whole grains, eggs, and dairy 5.

Iodine

Iodine is essential for making thyroid hormones—which control metabolism, protein production, and enzyme activity—and are vital for fetal and infant brain and bone development 7.

In adults, iodine deficiency can cause goiter, hypothyroidism, reduced mental function, lower work productivity, and in chronic cases, a higher risk of follicular thyroid cancer 7.

Iodine levels can be measured in urine. Urinary iodine levels show if intake is adequate: 100+ mcg/L for children/adults, 150+ mcg/L for pregnant women, and <100 mcg/L indicates inadequate iodine intake, with <20 mcg/L considered severe deficiency 7.

Top whole-food sources of iodine include cod, nori (seaweed), oysters, and iodized table salt. Yogurt and milk can be good sources of iodine, but the iodine content depends on whether the cow receives iodine supplements 7.

Folate (Vitamin B9)

Folate, sometimes called vitamin B9, helps make DNA and RNA, supports amino acid metabolism, and enables proper cell division. 

Signs and symptoms of folate deficiency in adults include megaloblastic anemia (causing weakness, fatigue, difficulty concentrating, irritability, headache, heart palpitations, and shortness of breath), sore or ulcerated tongue and mouth, changes in skin, hair, or nail color, gastrointestinal issues, birth defects in offspring, and high homocysteine levels 8.

Folate status can be assessed using blood folate levels and functional indicators like plasma homocysteine, which rises when folate is low, though it can also be affected by other factors 8.

Excellent sources of folate include beef liver, spinach, black-eyed peas, asparagus, Brussels sprouts, and romaine lettuce 8.

Vitamin D

Vitamin D helps the body absorb calcium and phosphate, supports bone growth and remodeling, prevents bone diseases like rickets and osteomalacia, protects against osteoporosis, and influences inflammation, cell growth, and immune function 9.

In adults, vitamin D deficiency can cause osteomalacia, leading to weak bones, bone pain and deformities, muscle spasms, hypocalcemic seizures, and dental problems 9.

Vitamin D status is mainly assessed by measuring serum 25(OH)D, which reflects vitamin D from food, supplements, and sunlight. Levels below 30 nmol/L (12 ng/mL) indicate deficiency, 30–50 nmol/L (12–20 ng/mL) may be inadequate, and 50 nmol/L (20 ng/mL) or higher is generally sufficient. Lab tests can vary, so standardized methods are recommended 9.

Though it’s easiest for most people to get their daily vitamin D from safe sun exposure, these foods can provide a lot in the diet: cod liver oil (by far the best food source), trout, salmon, and mushrooms exposed to UV light 9.

Vitamin B12

Vitamin B12 is essential for nervous system health, red blood cell production, and DNA synthesis, acting as a cofactor in key reactions that support methylation and energy metabolism. A deficiency can lead to fatigue, nerve problems, enlarged red blood cells (megaloblastic anemia), tongue inflammation, heart palpitations, and low blood cell counts, but symptoms may take years to show 10.

Vitamin B12 status is usually checked with blood tests—levels below 200–250 pg/mL suggest deficiency, and high methylmalonic acid (MMA) can confirm it when B12 levels are borderline 10.

Foods rich in vitamin B12 include beef liver, clams, oysters, nutritional yeast, salmon, tuna, and ground beef 10. Vegans and vegetarians typically need to take B12 supplements.

Bottom Line: Micronutrients like iron, vitamin A, zinc, iodine, folate, vitamin D, and vitamin B12 are critical for health, but because no single test is perfect, doctors often combine lab results with diet, symptoms, and risk factors to identify and address deficiencies. 

Note that some micronutrients—like calcium, magnesium, copper, and potassium—are notoriously hard to test for because their levels in blood don’t reflect their actual levels in the body. In general, doctors don’t bother to test these.

Food First, Micronutrient Tests When Needed

Micronutrients are essential, but testing has real limits. Unless you’re at higher risk of deficiency—or showing clear signs—broad panels often add more confusion than clarity. A nutrient-dense diet, good gut health, and attention to symptoms usually go further for everyday health than chasing perfect lab numbers.

If you’d like more personalized guidance, the experienced clinicians at our virtual clinic can help. They work with patients every day to uncover root causes of symptoms, optimize nutrition, and design sustainable health plans that match individual needs.

The Ruscio Institute has developed a range of high-quality formulations to help our clients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you. The information on DrRuscio.com is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment.