6 Essential Blood Markers Your Doctor Isn’t Testing

General Health

written by:

Emily Hage, MS, RD

Functional labs include essential blood markers that your conventional doctor is likely not testing. Have you ever gone to your doctor with a concern about certain symptoms, had routine lab work done, and been told that you’re fine because everything looks normal? While you may feel relieved to hear that everything looks “normal,” you may still be sensing that something is off. We have many clients come to us feeling dismissed and concerned about persistent symptoms, despite having their blood work come back normal at their doctor’s office. 

How Functional Labs Differ from Conventional Labs

At Birchwell, we utilize functional lab testing as both a preventive and investigative tool. Blood labs help us to identify the root cause of your symptoms and correct deficiencies and imbalances proactively, rather than taking the conventional approach of waiting until your routine blood markers are out of range or present as a diagnosis or disease.

Functional lab testing assesses blood work results based on “optimal” ranges rather than the standard “normal” lab ranges that often differ from lab to lab and can be based on stale data that do not reflect the most recent research. Using optimal ranges allows us not only to spot issues and trends before they become problematic but also to create an individualized plan to optimize your health.

When a practitioner on our team walks you through your results, it can be truly empowering to gain a deeper understanding of your body. Depending on your individual case and symptoms, we may incorporate GI Map stool testing, DUTCH hormone testing, micronutrient testing, and/or mold testing, along with comprehensive blood work. This advanced testing allows us to gain an in-depth understanding of your health and implement an individualized healing plan involving nutrition, supplementation, and lifestyle recommendations that are practical and attainable for you personally.

This article will walk you through a few examples of blood markers we consider essential. Note: this is far from an exhaustive list of all the markers we include and deem equally crucial for health optimization.

1. Ferritin

Ferritin is a measure of the body’s iron storage capacity and is a more sensitive marker of iron status. While a complete blood count (CBC) panel included on routine blood work can pick up on existing iron deficiency anemia, ferritin can detect iron deficiency long before it becomes anemia. Iron deficiency without anemia (IDWA) is the most common mineral deficiency. IDWA can arise before any changes are detected on a CBC (with vague symptoms that are easily associated with other conditions). Beyond its role in identifying early iron deficiency when low ferritin levels are present, elevated serum ferritin can indicate acute and chronic levels of inflammation in a variety of conditions.

Along with ferritin and a standard CBC panel, the iron labs we order include total iron, transferrin, total iron-binding capacity (TIBC), transferrin saturation, and unsaturated iron-binding capacity (UIBC). Together, these markers provide a more comprehensive picture of changes in iron status.

> The optimal range we aim for: Ferritin 60-150 mg/mL (depending on gender and menstrual status)

2. Homocysteine & MMA

Homocysteine is an inflammatory marker and amino acid found in the blood. It requires B vitamins (B12, B6, and folate) to undergo a recycling process to create proteins in the body. When this recycling doesn’t function effectively or the methylation process required is impaired, homocysteine builds up in the blood. Elevated homocysteine can indicate the presence of inflammation, a deficiency in B vitamins, or a mutation in a gene required for proper methylation. It can also increase the risk of heart disease, blood clotting, and stroke. In many cases, homocysteine can be balanced with a nutrient-dense diet and supplementation with a methylated form of B vitamins for optimal absorption.

Vitamin B12 (cobalamin) is essential for several body processes, including the formation of red blood cells and DNA, energy production, mood, and supporting healthy hair, skin, and nails. We use methylmalonic acid (MMA) to measure B12 depletion since elevated MMA has been identified as a more sensitive indicator of B12 deficiency than B12 itself. MMA production in the body tends to increase when B12 levels begin to drop. Serum B12 alone may be insufficient at detecting a functional deficiency, since it may be in a normal range in early-stage B12 deficiency.

> The optimal range we aim for: Homocysteine <7.20 umol/L; MMA 0.10-0.50 nmol/mL

3. Full thyroid panel

The most commonly ordered marker to assess thyroid function is Thyroid Stimulating Hormone (TSH). This is a hormone secreted by the pituitary gland that signals your thyroid gland to produce T3 and T4–the two hormones released by the thyroid that play a key role in regulating metabolism, energy levels, body temperature, cardiac function, and many other physiological processes. The problem with only looking at a TSH level is that it’s an indirect measure and doesn’t provide the full picture of how the thyroid gland is functioning.

To get the full story, we assess free and total T4, along with free, total, and reverse T3. The majority of hormone produced by the thyroid is T4 which is a mostly inactive precursor to T3. Free T3 measures active thyroid hormone and gives us a better understanding of the extent to which thyroid levels are influencing your metabolism. The body sometimes converts T4 into reverse T3 (inactive form) rather than free T3 (active form). Looking at the ratio of free T3 to reverse T3 may help to uncover the effectiveness of the conversion process of T4 into active T3. Additionally, we measure thyroid peroxidase (TPO) and anti-thyroglobulin (TG) antibodies to detect indications of autoimmune thyroid disorders such as Hashimoto’s.

> The optimal range we aim for: TSH 1.8-3.0 uU/mL; Free T4 1.00-1.50 ng/dL; Total T4 6.0-11.9 ug/dL; Free T3 3.00-3.5 pg/mL; Total T3 90.0-168.0 ng/dL; T3 Uptake 27.0-35.0%; Reverse T3 10.0-25.0 ng/dL; TPO Ab 0.0 IU/mL; TG Ab 0.0 IU/mL

4. Fasting insulin

Insulin is a hormone that helps to maintain blood sugar balance and keep glucose levels in check when functioning properly. After a meal, insulin transports glucose into cells to be used for energy and stored in the liver and muscles as glycogen for later use, lowering blood sugar levels back to baseline. When this process is impaired, and cells stop properly responding to insulin, they become insulin resistant. In insulin resistance, blood sugar remains elevated and the body produces more insulin in an attempt to bring glucose back to normal levels. Over time, this impaired insulin sensitivity can lead to type II diabetes, polycystic ovary syndrome (PCOS), metabolic syndrome, cardiovascular disease, nonalcoholic fatty liver disease, and weight gain.

At annual visits, doctors typically measure fasting blood glucose without including fasting insulin. Monitoring insulin levels can help with the early detection of insulin resistance and prediabetes before they become a more problematic condition. Insulin levels can become elevated well before changes in blood sugar levels occur, which is why fasting insulin is one of the essential blood markers to include. With diet and lifestyle changes, we can improve insulin sensitivity (the ability for your cells to properly take up glucose).

> The optimal range we aim for: Fasting insulin 3-8 uIU/mL, 18-48 pmol/L

5. Cardiovascular risk factor panel (Apo B, LP(a), hs-CRP)

A traditional lipid panel to measure cardiovascular risk usually consists of total cholesterol, low-density lipoprotein (LDL aka “bad cholesterol”), high-density lipoprotein (HDL or “good cholesterol), and triglycerides. In addition to this standard panel, we also include the essential blood markers Apo-B, LP(a), and hs-CRP to more sensitively assess cardiovascular risk.

  1. Apo B – ApoB is the main protein component found in low-density lipoproteins (LDL) and plays a vital role in the buildup of LDL cholesterol in blood vessels. ApoB is becoming a preferred marker for the detection of cardiovascular risk as growing research indicates it can provide a more reliable prediction of a cardiac episode than LDL and other lipid markers. LDL alone can underestimate risk in certain cases, which is why a comprehensive cardiovascular panel is needed.
  2. LP(a) – Lipoproteins are protein molecules that transport cholesterol and other fats in the blood. Lipoprotein (a) or LP(a) is a type of LDL cholesterol that is an independent and causal risk factor for atherosclerotic cardiovascular disease. An elevated LP(a) level increases the likelihood of blood clotting and plaque buildup in blood vessels, interfering with blood flow to vital organs and increasing the risk for a cardiac episode or stroke.
  3. hs-CRP – The liver makes C-reactive protein in response to inflammatory molecules. Elevated CRP signals that there is inflammation occurring somewhere in the body, but doesn’t indicate the location or cause of that inflammation. CRP is correlated with an increased risk of myocardial infarction. A standard CRP test is mainly used to identify inflammation in acute conditions and monitor chronic disease severity. In comparison, an hs-CRP test can more sensitively measure a slight increase within the normal range, helping to detect much lower levels of inflammation.

> The optimal range we aim for: Apo B 52-109 mg/dL; LP(a) <14 mg/dL; hs-CRP <0.5 mg/L

6. Zinc and copper

Zinc and copper are trace minerals and essential blood markers that operate synergistically for immune system function, nervous system function, metabolism, cardiovascular health, and maintaining oxidative balance in the body. At optimal levels, they may help offer protection against free radicals as components of an antioxidant enzyme called superoxide dismutase. Zinc and copper, along with vitamin C, are needed for collagen production (the most prevalent protein found in the body and a key component of connective tissue and bones). Along with its crucial role in the immune system, skin health, and wound healing, zinc is needed for cell growth and DNA synthesis, hormonal and reproductive health, thyroid function, vision, taste, smell, metabolism, and insulin synthesis.

Zinc and copper have an antagonistic relationship–an excess of either mineral can cause a deficiency in the other. High levels of zinc can block copper absorption in the small intestine, leading to a copper deficiency. Copper is needed for iron absorption and red blood cell formation, which is why a copper deficiency can lead to iron deficiency anemia. Copper also plays a crucial role in brain health and development, cardiovascular health, and nervous system function. We assess serum zinc and copper levels to maintain an optimal ratio between the two minerals.

> The optimal range we aim for: Zinc 0.5-1.0 mcg/mL; Copper 0.6-1.8 mcg/mL

Essential Blood Markers – Final Thoughts

Functional lab testing can provide a wealth of information in comparison to standard blood labs. The comprehensive range of essential blood markers and optimal lab ranges used in functional testing allows us to take a proactive rather than reactive approach to your health.

At Birchwell, we team you up with a Registered Dietitian who specializes in functional medicine. They take the time to understand your health from the inside out using advanced lab testing, nutrition, supplements, and lifestyle changes.

Interested in learning more? Book a non-obligation, complimentary discovery call to chat with one of our practitioners and see if our functional health consulting is right for you.


Feeling better is possible. Meet with one of our practitioners to find out if 1:1 Functional Medicine Consulting is right for you.

Book a complimentary discovery call

Anya is a Registered Dietitian, Functional Medicine Practitioner and founder of Birchwell, a virtual integrative health clinic based in New York City.

She specializes in helping her clients identify the root cause of their health concerns through advanced lab testing and her comprehensive assessment. She uses functional diet, supplement, and lifestyle strategies to address any imbalances in the body. Through her integrative and functional nutrition practice, Anya has helped hundreds of adult women and men fix their gut health (e.g. SIBO, reflux, candida, etc.), balance their hormones (e.g. PCOS, peri-menopause, estrogen dominance, etc.), clear their acne or eczema, boost their energy and performance, combat anxiety and depression, improve their body composition, reduce their joint pain - and more.

Anya Rosen, MS, RD, LD, IFNCP, CPT

About the founder


on the



recently on the journal