Causes of Chronic Fatigue | A Functional Medicine Perspective

by Dr. Kilcup | Jun 21, 2018 | Adrenal Fatigue, Articles, Chronic Fatigue Syndrome, Depression, Fatigue

Causes of Chronic Fatigue

Causes of Chronic Fatigue

Almost every patient I see complains of some degree of chronic fatigue. As a functional medicine doctor I have to find out what is causing this fatigue if I’m going to help. The possible causes of chronic fatigue are many. Most of the time my patients with chronic fatigue have more than one source contributing to their chronic fatigue. I will cover some of the most common causes.

Causes of Chronic Fatigue | Nutrient Deficiency

It’s just common sense that if a person doesn’t have the nutrients needed for energy they will have fatigue. Once these deficiencies are identified fixing them is easy! However, discovering nutritional deficiencies is not simple. The best test for determining a deficiency varies depending on what kind of nutrient we are looking for. For example, if we want to know about magnesium the standard test for serum level of magnesium is meaningless. The test that is helpful tests red blood cell magnesium. As you might expect, this test measures the amount of magnesium in the red blood cells. Since red blood cells live for about three months, knowing the amount of magnesium in these cells gives you a good idea of the current status of magnesium in the blood.

Sometimes simple levels of a nutrient can be misleading, because some people require very different amounts of a nutrient than the “average” person. This is where functional medicine testing is so valuable. Instead of testing for the nutrient we test for things that show up if the body is lacking that nutrient.

Organic acid testing is an excellent example of testing for things that show up when a nutrient is lacking. The figure below illustrates the way the body is supposed to work. Let’s say that “A” represents a molecule (Pyruvate) from a carbohydrate that you ate and it needs to be turned into energy. The body does this in stages (“B”, “C”, and “D”) converting the carbohydrate into something called ATP. ATP is the fuel of the body. In order to convert a carbohydrate into ATP specific nutrients are required. If the needed nutrients are not supplied ATP is not created. In this illustration all the nutrients are supplied and beautiful biochemistry happens!1

In this next illustration the nutrients needed to convert the carb to energy is missing and two things happen. One is obvious, a lack of energy but the other is that “A” (Pyruvate) shows up in the urine because its wasn’t converted to energy. Pyruvate is an organic acid. These organic acids can be discovered in the urine and this can tell us what nutrients are needed.

Causes of Chronic Fatigue


This next illustration gives you more specifics. Don’t worry, you don’t need to understand everything here. In fact interpreting this test is complicated. The reference I use is over a thousand pages long. I just want you to see that, when trying to determine whether a person’s fatigue is coming from the lack of nutrients, testing for organic acids is invaluable.

Causes of Chronic Fatigue


Causes of Chronic Fatigue | Infections

Infections from viruses like Epstein Barr, bacteria like Borrelia Burgdorferi, and fungi like Candida are examples of infections that produce fatigue. Often these pathogens go un-diagnosed and as a result I’ve had patients who have suffered for years with infections that are causing chronic fatigue. The symptoms of many of these infections are similar, so testing here is very important.

 Causes of Chronic Fatigue | Toxins

Heavy metals like Mercury, Lead and Cadmium, mycotoxins from mold or phthalates are all common toxins that can cause chronic fatigue. These toxicities can occur two ways. The first is obvious–being exposed to a large amount of a toxin or exposure on a daily basis. The second way is when a person’s body is unable to detoxify the toxins. The worst case scenario is when both of these occur at the same time.

Detoxing is different depending on what toxin or toxins are the problem and the detoxing capacities of the patient. Again testing is critical to discovering if and why toxins are a problem.

 Causes of Chronic Fatigue | Hormones

Imbalances in cortisol, thyroid hormonesestrogen, progesterone and melatonin can cause chronic fatigue. A hormonal imbalance is generally secondary to some other issue. Intestinal dysfunction, toxins, infections and nutrient deficiencies can all lead to hormone imbalance.

If you’re paying attention here you may be thinking, “I bet people with chronic fatigue have more than one thing wrong.” You are absolutely right. These things can have a domino effect, and there is no drug or pile of drugs that will do anything to correct any of this.

 Causes of Chronic Fatigue | Food Sensitivities

Food sensitivities are not allergies. They are immune reactions to certain foods that cause the body to treat those foods as if they were pathogens. This hyper-immune reaction to foods is generally secondary to intestinal problems like leaky gut syndrome. I’ve had patients with extreme chronic fatigue find complete relief after figuring out their food sensitivities.

 Causes of Chronic Fatigue | Diet

I don’t write about diet as much as I could. Most of my patients have excellent diets before they come to me. They have eliminated junk food, and eat mostly unprocessed, clean, whole foods. Not only will eating junk food (high in sugar, processed, full of chemicals) cause fatigue, but it will also hurt the gut, create nutrient deficiencies, and leave a person wide open to infection by feeding pathogens and suppressing the immune system.

Causes of Chronic Fatigue | Neurotransmitter Imbalance

An imbalance in neurotransmitters can cause chronic fatigue. There are nine neurotransmitters we can test for. A functional medicine approach to neurotransmitter imbalance is far more than just prescribing an antidepressant. We find out which NTs are out of range, low or high, and then get them balanced with the right nutrients. Here again if the NTs are out of balance, something else is generally causing that. Most of the NTs are made in the gut, so we want to make sure that the intestinal tract is working properly.

Causes of Chronic Fatigue | A Functional Medicine Perspective

I began this article telling you that almost every new patient I have complains of some degree of chronic fatigue. I hope that now you can see why. So many problems result in fatigue. To make matters worse, a lot of these problems cause other issues that can make the fatigue worse.

There are no shortcuts to getting my chronic fatigue patients better. Because chronic fatigue has so many possible causes, comprehensive testing is mandatory. We must find the root of the problem so we can fix it.

As always, I welcome your questions or comments. If you live in the USA and have chronic fatigue, I can help you.

Show 3 Footnotes

  1. Adapted from Genova Diagnostics interpretation guide for Organic
  2. Adapted from Genova Diagnostics interpretation guide for Organic
  3. Adapted from Genova Diagnostics interpretation guide for Organic

Darrell Kilcup, DC, CFMP

Hi there! I’m Dr. Kilcup. You know that health problem you’ve been dealing with – the one that doctors can’t seem to solve, that’s stealing way too much of your time, energy and joy? I can help you get to the bottom that. I am passionate about using the best of science and nutrition to find and fix root causes of health issues. Start your journey towards healing and relief today.

Ways We Can Work Together





All Reviews 5.0google logoGoogle 5.0
Overall Rating
5.0 4 reviews
I have been using the Hyperbaric Oxygen Therapy for the last few weeks and It has helped me so much. I struggle quite a bit with work related stress. When I'm in the chamber I feel completely relaxed, so much so that I can bring my laptop inside and work without stressing. The calmness I feel in the chamber lasts for the remainder of the day as well. I have found too, the more consistent I am with sessions throughout the week the better I feel. The office staff seems well trained in running the tanks too, so I feel safe. I see Dr. Kilcup as well for my brain and gut health. Until now, I don't think I've ever known what "normal" or "healthy" feels like. Thank you all, sincerely!
read more
Mike Kutz Avatar
Mike Kutz
6 months ago
Dr. Kilcup is a pleasure to work with. His office is beautiful! I can’t wait to try his hyperbaric chambers!
read more
Sarina Gomez Avatar
Sarina Gomez
9 months ago
Darrell is highly knowledgeable and really gets to the root of the problem. Unlike a lot of doctors, Darrell doesn't just throw prescriptions at issues. He will test and test - digging for the cause and then working on fixing the issue. He and his staff are professional, courteous, and a joy to be around.
read more
Kevin Miller Avatar
Kevin Miller
1 year ago
I am very grateful to have found Dr. Kilcup and be his patient for the last couple of years. He has helped me restore my health back after being exposed to toxic mold for years. He helped identify and treat all of my symptoms I was experiencing and address the root problem. I was looking for the right person who could help me heal with natural therapies and supplements and Dr. Kilcup was the perfect fit. Every appointment and session was necessary and one step towards all the progress I made. Dr. Kilcup is a great functional medicine doctor who was also an advocate for my own health and well-being. I never received any care or attention to detail from other Doctors in past experiences except with Dr. Kilcup. Anyone who is seeking a holistic path towards healing or improving their own health should see him.
read more
Ciara Wakley Avatar
Ciara Wakley
1 year ago