Essential Nutritional Tests Registered Dietitians Can Order

Registered dietitians (RDs) are personal food experts for individuals trying to eat healthier and those with nutrition-related medical concerns. They translate complex nutritional science into practical, real-life advice using research-backed methods. 

RDs build balanced meal plans tailored to patients’ lifestyles, health goals, and food preferences. Personalized nutrition is an evolving field that may contribute to improved dietary habits. 

Did you know that dietitians can sometimes order lab tests? 

This article explores the role of registered dietitians in modern healthcare and the nutrition-related tests they may order or interpret to support dietary and lifestyle interventions.

The scope of practice and the ordering of lab tests by RDs varies by state. Consult local regulations to confirm.

Understanding Nutritional Testing

Nutritional testing includes nutrition assessments and lab tests that provide insights into an individual’s dietary patterns, nutrient status, and overall wellness. These tests can help dietitians tailor nutrition recommendations based on factors such as dietary intake, health history, and lifestyle. These assessments typically consist of blood, urine, stool, or genetic testing. 

Nutritional tests help dietitians create customized plans that may help reduce the risk of chronic diseases, meet the body’s nutritional demands, optimize healthy weight management, or better manage diabetes, celiac disease, food intolerances, high blood pressure, and other chronic conditions.

Core Nutritional Tests Ordered by Registered Dietitians

Core nutritional tests RDs can order (or in collaboration with a healthcare team if required by local regulations) are summarized below.

Comprehensive Metabolic Panel 

A comprehensive metabolic panel (CMP) is a group of diagnostic blood tests that analyzes the body’s overall metabolic health. They include electrolytes, blood sugar (glucose), protein, liver health markers, kidney health markers, and more. 

CMP tests assess various metabolic markers and may provide useful information related to kidney and liver function, blood sugar levels, and electrolyte balance.

CMP analyzes metabolic markers including sodium, potassium, calcium, carbon dioxide, chloride, blood urea nitrogen (BUN), creatine, glucose, total protein, albumin, aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), and total bilirubin. 

Lipid Profile

Lipid profiles are blood tests that measure cholesterol and triglyceride levels, which are important indicators of heart health.Lipid panels generally include total cholesterol, low-density lipoprotein (LDL) cholesterol, very low-density lipoprotein (VLDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides.

Hemoglobin A1C

Hemoglobin A1C (HbA1c) is a blood test and a highly important marker of diabetes management (blood sugar control over time). It measures the glycosylated form of hemoglobin in red blood cells, which forms when hemoglobin molecules bond to sugar in the bloodstream. 

HbA1c reflects the average blood glucose concentration over the past 2–3 months and may provide insight into long-term blood sugar trends.

Vitamin and Mineral Panels

Vitamin and mineral panels assess nutrient levels, which may provide insights into overall nutritional status. Maintaining adequate nutrient intake is important for general well-being.

Examples of vitamin and mineral levels these panels can screen for include:

• Vitamins: vitamin C, vitamin D, vitamin A, vitamin K, vitamin E, vitamin B12, vitamin B6, folate, and other B vitamins 
• Minerals: iodine, selenium, iron, zinc, copper, magnesium, manganese, calcium, potassium, and more

Dietitians may also be able to order lab tests that assess levels of amino acids, choline, electrolytes, omega-3 docosahexaenoic acid (DHA), omega-3 eicosapentaenoic acid (EPA), coenzyme Q10 (CoQ10), lipoic acid, and many other nutrients.

Thyroid Function Tests

Thyroid function tests, including thyroid-stimulating hormone (TSH), free triiodothyronine (T3), and free thyroxine (T4), measure metabolic function and screen for (or help better manage) hypothyroidism (underactive thyroid), hyperthyroidism (hyperactive thyroid), and other thyroid conditions that negatively affect metabolic rate. 

Diet and nutrition affect thyroid health, which is why dietitians might order thyroid function tests. For example, low dietary iodine intake can lead to reduced thyroid hormone levels and a slowed metabolism. 

In many cases, these tests are ordered in collaboration with a physician or another licensed provider.

Specialized Nutritional Tests

There are several specialized nutritional tests dietitians might order to better plan effective nutritional interventions.

Food Sensitivity and Allergy Testing

Food allergies affect 8% of children and 11% of adults. Food sensitivity and allergy testing, including IgE and IgG tests, may help identify potential food-related immune responses. A healthcare provider should be consulted for proper interpretation and guidance.

Food allergies mediated by IgE antibodies release histamines and other chemicals, causing sometimes severe reactions. Examples include itching skin, swelling, digestive problems, and anaphylaxis. 

Food sensitivities are often mediated by IgG and can cause gas, bloating, diarrhea, cramping, nausea, constipation, and other gastrointestinal symptoms. They may also lead to mild symptoms of an allergic reaction (itching, swelling, nasal congestion, headaches, etc.).

Note: IgG-based “food sensitivity” tests are controversial and not universally accepted by the medical community. Interpretation should be done by a qualified healthcare provider in conjunction with clinical assessment.

A dietitian might recommend blood tests, skin prick testing, an elimination diet, or oral food challenges to pinpoint the foods causing negative symptoms and create a safe, symptom-free meal plan. 

It’s important for patients to consult a healthcare professional regarding serious or suspected food allergies or intolerances.

Gut Health Assessments

Maintaining a healthy gut is strongly associated to overall physical and mental health. Microbiome testing analyzes gut bacteria composition and may provide insights into digestive health, but it’s still an evolving field. Intestinal permeability tests help providers screen for leaky gut and malabsorption, which can influence an RD’s diet and supplement recommendations. However, these tests aren’t considered diagnostic.

Nutrigenomics Testing

Genetic variations may affect nutrient metabolism. Nutrigenomics testing analyzes genetic variations that may influence how individuals metabolize certain nutrients. In other words, it demonstrates how certain genes likely interact with food and nutrition. Dietitians may use this information to help inform individualized diet plans.

For example, it may help point out which foods and nutrients to cut back on and which to supplement with—particularly in individuals with metabolic genetic disorders. However, nutrigenomics is a developing science and should be interpreted with caution.

Oxidative Stress and Inflammation Markers

Other highly effective nutritional tests dietitians may order include those that screen for oxidative stress and inflammation. Examples include C-reactive protein (CRP) tests and antioxidant testing.

CRP levels are a general marker of inflammation. Some research suggests a connection between inflammation and various health conditions, but individual results should be interpreted by a healthcare provider. CRP helps predict long-term health outcomes.

Oxidative stress tests measure how free radicals impact the body by measuring damaging radicals compared to antioxidative nutrients (glutathione, vitamin C, vitamin E, carotenoids, etc.)

Interpretation of these markers should be done in conjunction with other clinical assessments.

The Process of Nutritional Testing With a Registered Dietitian

The nutritional testing process with an RD typically begins with an initial consultation and medical history review. They evaluate body weight and body mass index (BMI) and discuss past diagnoses, medications, and lifestyle habits (particularly usual diet and exercise regimens). 

RDs may then select appropriate tests, interpret the results, and develop personalized nutrition plans that match patients’ specialized needs. They follow up as often as needed to monitor progress and adjust meal plans as needed.

Benefits of Nutritional Testing

Examples of the potential benefits associated with implementing nutritional testing by RDs may include:

• Early detection of nutritional imbalances
• Enhanced disease management
• Targeted nutritional interventions for specific health concerns
• Improved efficacy of dietary changes
• Enhanced overall well-being and quality of life
• Cost-effectiveness in long-term health management

Nutritional testing and personalized meal planning may support overall well-being by helping individuals make informed dietary choices. However, individuals should consult their healthcare provider before making any changes to medication or medical care.

Limitations and Considerations

Potential limitations and considerations linked to nutritional tests include variability in test accuracy and interpretation, cost, and differing insurance coverages. Furthermore, potential ethical considerations exist related to genetic testing. 

Providers must order the most appropriate tests based on patients’ personalized needs and use context when interpreting the results. 

Case Studies: Success Stories With Nutritional Testing

Dietitians and their patients can integrate nutritional test results into lifestyle habits to optimize overall health and well-being. 

For example, individuals diagnosed with iron-deficiency anemia can increase their intake of iron-rich foods or take a dietary supplement containing iron. People with celiac disease or gluten sensitivity can learn ways to safely eliminate gluten from their meal plans.

Lifestyle modifications that may complement nutritional interventions include reducing stress, cooking at home instead of dining out, controlling calories, getting more sleep, boosting exercise, and taking specific dietary supplements. Regularly monitoring diet and lifestyle progress with nutritional retesting when needed may be helpful for optimal health. 

The Future of Nutritional Testing

The future of nutrient testing involves emerging technologies for nutrition assessments, integration with wearable devices and AI, and assessing nutrient intake via nutrition-related mobile apps.

Other potential new trends include sport nutrigenomics (personalized nutrition plans designed for athletes by sports dietitians based on genetics) and nutrition testing’s vital role in preventive healthcare, advanced personalized nutrition, and longevity. 

Some researchers suggest that laboratory analytics, biocomputing, newer nutrigenetics, and using foods and supplements may help personalize nutrition. However, this is a rapidly evolving area requiring more research.

FAQs

The following are answers to frequently asked questions regarding nutritional testing.

How often should you undergo nutritional testing?

While dietitians and other medical professionals determine how often each patient should undergo nutritional testing based on their unique situation, it’s common to order such tests every three months, six months, yearly, or as needed based on symptoms and risk factors. 

Can you order these tests without a registered dietitian?

Dietitians (in certain jurisdictions), doctors, and many other healthcare professionals can order nutritional tests. Some cash-based lab-testing facilities don’t require a medical professional’s order. 

How long does it take to see results from dietary changes?

Depending on the reason for dietary changes and the specific changes patients make, they might experience immediate results—such as more energy or fewer allergy symptoms. However, it could take a few weeks or months to notice significant differences in the way their bodies function, feel, or look after making dietary adjustments or beginning dietary supplements. 

Are there any risks associated with nutritional testing?

Nutritional tests are safe diagnostic tests with minimal to no risks. However, blood tests can cause redness or tenderness at the injection site, and food allergy testing may cause minor allergic reactions. 

Key Takeaways

• Nutritional testing ordered by dietitians used for personalized meal planning or disease management can help dramatically enhance overall health and well-being.
• Patients should consult with a registered dietitian for nutrition test recommendations and personalized diet plans. 
• Start implementing nutritional tests, read our related articles to further explore nutrition topics, and leave comments with questions or share your experiences below.