Labs “normal?” Why optimal lab ranges say otherwise

optimal lab rangews

Many times, hearing your lab results are normal can be a relief. But if you still have symptoms that no one can figure out, getting that same news can be worrisome and frustrating. From a functional medicine perspective, relying solely on normal reference ranges to interpret labs isn’t enough. We want to look at results through the lens of reference ranges, your clinical signs and symptoms, and what the optimal lab ranges are for each lab marker.

My physician says my labs are normal, end of conversation. But I still have symptoms and am not sure what to do

I always ask clients to get a copy of all lab work. Patients have a legal right to their medical records, and most providers will provide lab results to you via a portal or a printout at your appointment. (Speak up and ask!) Not only is it helpful to know your numbers, it’s also helpful to track values over time to identify trends that are headed in the wrong direction. That way, you can get things back on track before true disease develops. (A good example of this is fasting blood glucose that continues to climb.)

Conventional lab testing historically is used to identify and diagnose disease and pathology. Here’s the reason why it’s so important to get a copy of your results: reference ranges given by labs are reflective of 95% of the U.S. population. But because the U.S. population at large has a lot of health issues like obesity, diabetes, and cardiovascular disease, they’re not always the best measure of your personal vitality. Why? Because as the population has gotten sicker, the reference ranges are incorporating more and more of that info into guiding what’s “acceptable” or “normal.”

Why where you fall within the reference range matters

The problem with blindly using reference ranges as a catch-all for “normal?” While reference ranges are necessary and a great guiding framework to identify and diagnose, through a functional lens, we can also use them proactively to reverse dysfunction before full-blown disease develops. Where you fall within the reference range can be significant information to understanding how the systems of the body are working together, identifying the root cause of any dysfunction, and planning interventions to help achieve health goals.

For example, your fasting blood glucose results can look fine within the context of references. However, it could still be suboptimally high or low enough to warrant discussion and lifestyle changes. That’s why I like to review clients’ labs and look at where their numbers are relative to the optimal range for each specific test.

What do you mean by optimal lab ranges and results?

What’s optimal for a given test exists within the normal reference range. Depending on the test performed, optimal lab ranges can be toward the high end, low end, or in the middle of the reference range. I’ll get into an example below, but I also recommend the book Blood Chemistry and CBC Analysis: Clinical Laboratory Testing from a Functional Perspective by naturopathic doctors Dicken Weatherby and Scott Ferguson, first published in 2002. It’s a great resource to learn more on the meaning of optimal.

Here’s an example of complete thyroid testing and evaluation of optimal ranges

Especially in suspected or diagnosed cases of hypothyroidism, it’s important to know a few things. There are multiple thyroid hormones and helpful lab tests for each of these hormones. When some healthcare providers test thyroid function, they only measure thyroid stimulating hormone, or TSH. TSH is released by the anterior pituitary (located in the brain) and helps coordinate and modulate the thyroid’s release of hormones. 

In some people, TSH will be elevated enough to indicate hypothyroidism. But sometimes, it’s not so straightforward. Other thyroid hormones can be helpful to look at. This includes free thyroxine (free T4), free triiodothyronine (free T3), and reverse T3 (rT3)—as well as thyroid antibodies that can be present with the thyroid autoimmune conditions Hashimoto’s and Graves disease. Evaluating free T4 and T3 can be tricky. Your results may come back low-normal but within the stated range. However, those numbers may not be what’s best for your body and you could have hypothyroid symptoms as a result. We call this “subclinical hypothyroid.” Comparing to past testing, if available, can be helpful. But as a general rule, most people tend to feel best in the upper third of the lab reference range… that’s what’s optimal.

Ratios are important to blood work. How come I don’t see those on my results?

Because hormones are all interconnected, it’s critical to check how they’re doing in relation to one another. Functional medicine teaches us that ratios are valuable. But sometimes these go uncalculated.

A great testament to the importance of ratios? Checking free T3 (the bioavailable form of our biologically active thyroid hormone) in relation to reverse T3 (rT3). Reverse T3 is exactly what it sounds like: the opposite of T3. It sits on thyroid receptors and blocks free T3 from getting where it needs to go. In some instances, this is a necessary function. But, for a variety of reasons, we can create too much rT3. (Like excess cortisol from stress or calorie restriction.) When rT3 is high in relation to free T3, we can end up with hypothyroid symptoms but labs that look normal.

Another example of misleading lab ranges is estrogen and progesterone testing. That’s because test timing and ratios are key

Much before estrogen levels drop, its counter sex hormone, progesterone, lowers. In a lot of women, it slowly and steadily drops in their 30s. But lifestyle and other factors can cause a more precipitous decline. With estrogen still high or normal (and sometimes elevated due to xenoestrogens found in skincare products and other chemicals), this creates estrogen dominance, a relative imbalance heavy on estrogen versus progesterone. Estrogen dominance can be super uncomfortable, cause bloating, mood swings, weight gain, irregular periods, anxiety, and increase cancer risk.

Testing estrogen and progesterone on days 19 to 21 of your cycle is best. But just looking at the numbers isn’t enough for evaluating results. Calculating a progesterone to estradiol ratio can give a true picture as to whether or not you are dealing with estrogen dominance or if you have a hormone imbalance.

How do I talk with my doctor about optimal versus normal?

First, let’s acknowledge that traditional physicians and other healthcare professionals have diagnostic criteria and clinical guidelines they must follow. They’re still highly dedicated to their patients. And many also believe in the value of complete thyroid testing and discussing ratios.

But optimal lab ranges are largely a functional medicine belief and phenomenon. Depending on your physician’s or nurse practitioner’s training and openness to new ideas, he or she may or may not be willing to help order more testing and evaluate or treat based on low-normals and high-normals. 

In talking with your doctor, focus on the clinical symptoms you’re having and ask for additional testing. If your doctor isn’t open to this, you can work with a functional medicine coach. They help you grow your understanding of results, so you can better advocate on your behalf. You can also visit the Institute of Functional Medicine’s provider database to find a provider near you.  

Rachel Rotabi, PT, PN L1, AFMC L1
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