10 Causes of Fatigue–The Tests You Need & How to Heal!

The information provided in this post is for informational purposes only and should not be construed as medical advice.
It is not a substitute for your doctor's care plan or advice.

Tired all the time? Here are 10 Causes of Fatigue, the blood tests you need, and how to heal--from a pharmacist who's beaten fatigue herself.

{Fatigue can really be a problem for so many people. It was for me. I still have some issues with it but thanks to so much work on my health, it's a much smaller problem now.  

Today, Izabella Wentz is here to talk about some causes of fatigue and how to find out if these are problems for you. I met Izabella several years ago and immediately sensed her passion and knowledge. Her book was one of the biggest helps for me as I got on the road to recovery from chronic fatigue, Hashimoto's Thyroiditis, and more. I hope you find help and healing in this post.}

Fatigue vs. Tiredness

If you’ve experienced fatigue, you know there’s a difference between it and just being tired. Tiredness is what you feel when you think you need a nap. Fatigue digs in deeper–dragging on your motivation and emotional and physical energy.

Reasons for fatigue aren’t as obvious as those for tiredness. Simple tiredness might be explained by a late night of TV watching, an after-dinner espresso, or one or more kid-fueled interruptions during the wee hours.

Fatigue is more likely to settle in inexplicably.

Fatigue also doesn’t seem to be remedied by simply getting some extra rest and relaxation.

I experienced extreme fatigue for several years during my twenties. During that time, I needed to sleep at least 12 hours a night to be semi-functional, and I relied on near constant caffeine intake to keep me going.

It wasn’t until I was diagnosed with Hashimoto’s Thyroiditis at 27—and started to treat it with thyroid medications—that I began to experience some relief. Although even then, I was still frustratingly low on energy most of the time.

As a practicing pharmacist, I began to research emerging information on Hashimoto’s and possible underlying and/or concurrent conditions. What I discovered is that there are specific thyroid markers and several other factors that can perpetuate feelings of fatigue.

Addressing these causes of fatigue is what finally brought me the energy and motivation I had been lacking for so many years. I hope these strategies might help you, too!

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Tired all the time? Here are 10 Causes of Fatigue, the blood tests you need, and how to heal--from a pharmacist who's beaten fatigue herself.

10 Causes of Fatigue: The Factors That Matter Most

1. Out of Range TSH

Thyroid-stimulating hormone, or TSH, is the hormone that triggers your thyroid to make triiodothyronine (T3) and thyroxine (T4). Your TSH level will typically be tested to determine if you have a thyroid disorder and to give your doctor the information needed to dose thyroid medications, if needed.

The problem with testing for TSH starts with the test itself. When the “normal” reference range was first established, it was done so based on a group that included elderly patents and others with compromised immune function. Because of this, what’s normal according to most labs isn’t really what’s normal for a healthy individual.

The American College of Clinical Endocrinologists has established a new normal reference range with TSH falling between 0.3-3.0 mIU/mL. In my work, I’ve discovered that most people will feel their best with a TSH between 0.5-2 mIU/mL. The problem is that many labs still define normal as falling between 0.2-8.0 mIU/mL.

If you’ve had your TSH tested and received “normal” results and you’re still struggling with fatigue, I recommend revisiting your lab report. If your results fall outside of the new normal reference range, I encourage you to discuss this further with your doctor.

2. Low T3 / High Reverse T3

T3 is a trigger for your cells to produce more energy. If you are low in T3, it’s likely that you will be low in energy, too.

You can be low in T3 even if you are currently on thyroid medication. The most commonly prescribed thyroid medication, Levothyroxine, provides only T4, which is then converted within the body to T3. This conversion can be disrupted, however, by nutrient deficiencies, stress, and other factors. In this case, you will continue to feel drained despite a normal T4 level.

Another disruption of energy production can occur if you have elevated levels of a molecule called reverse T3. This molecule will cause your cells to slow down energy production.

If you are taking thyroid medication and still feel fatigued, it’s definitely worth reevaluating your Rx. A test of your T3 level and your reverse T3, if necessary, could reveal a need for a different pharmaceutical approach. One strategy is to try a T4/T3 combination. This can be accomplished by adding Cytomel to Levothyroxine, getting a compounded T4/T3, or trying Armour or Nature-Throid.

3. Low Vitamin D

Do you find that you feel generally better in the summer (when there’s more sun) and worse in the winter? You could have low Vitamin D levels.

Vitamin D is vitally important to energy and immune balance, and it’s even shown to help prevent autoimmunity. Direct sunshine, supplements, and certain foods are all sources of Vitamin D.

When you get your levels checked, you’ll want to see a number that falls between 60-80 ng/dl. Having an optimal vitamin D level is especially important if you’ve had mono because Vitamin D powers the cells that fight the virus.

4. Subtle or Undiagnosed Anemia

Fatigue, weakness, and cold hands and feet are a few symptoms of anemia. If you report these symptoms to your doctor, you will probably be advised to get a blood test to check your red blood cell (hemoglobin) levels.

In advanced cases, a diagnosis of anemia can be made based on the results of this test. Low Ferritin (a protein in your blood that stores iron), B12, and folate can all precede anemia. However, these issues won’t show up on a hemoglobin test.

The best step in this case is to have your ferritin, B12, and folic acid levels checked. As with TSH, there is some debate over optimal levels. For B12, a lab will typically identify “normal” as falling between 200-900 pg/mL, but I’ve found that anyone with a level below 800 pg/mL might benefit from supplementation.

When choosing a B12 supplement, be sure to get the methylcobalamin type, which absorbs better than the alternative.

A typical range for normal ferritin levels for women is between 12-150 ng/mL. For thyroid health, however, some experts consider the optimal range to be 90-110 ng/ml.

Folate can become deficient when we have the MTHFR gene mutation (see below) that prevents proper absorption of folic acid from processed foods and common supplements. In the case you have this gene mutation, you'll likely benefit from a more absorbable form of folate, such as methylfolate.

You should of course discuss any lab results with your doctor. However, I encourage you to also get a copy of the results for yourself and compare to the levels noted here.

5. Blood Sugar Imbalances

If you’re constantly feeling low in energy or you regularly experience severe dips in energy, it’s worth paying attention to your blood sugar. One way to test if blood sugar imbalances are behind your fatigue is to lower your carbohydrate intake and opt instead for some quality protein and fat and see how you feel.

Of course getting your fasting glucose level tested is another traditional way to check for blood sugar concerns.

6. Inefficient Digestion

Even perfectly functioning digestion demands a lot of energy. The process can be even more draining if you have an autoimmune condition, such as Hashimoto’s, and/or a gut infection or imbalanced gut.

Any efforts you make to improve your digestion are likely to reward you with an increase in energy. My personal favorite strategies for improving digestion include green smoothies (check out https://thyroidpharmacist.com/articles/how-a-green-smoothie-can-help-your-thyroid/ for my base recipe) and the digestive enzyme betaine with pepsin.

Betaine with pepsin can improve digestion and increase absorption of important nutrients such as B12, iron, and calcium.

Taking the CBC and CMP blood test can give clues that one is suffering from a lack of stomach acid.

7. Food Sensitivities

I’ve found that people with Hashimoto’s–including myself–often present food sensitivities. And the same is true in many autoimmune conditions. The most common sensitivities are to gluten, soy, dairy, egg, corn, and nuts.

A sensitivity can be revealed by completing an elimination diet or, in some cases, getting a blood test. Removing a food that you are sensitive to will not only help restore your energy, but might also eliminate other symptoms.

8. The MTHFR Gene

No, this isn’t a gene for cursing, but the methylene tetrahydrofolate reductase gene. We all have it, but only some of us (up to 50%) have a variation of it that can interfere with folic acid conversion.

Folic acid is the synthetic form of vitamin B9 in many supplements while folate is the natural form in foods. Folate is mportant to emotional and mental health and plays a role in producing energy.

People with the MTHFR gene variation could benefit from taking methylfolate, the activated form of folic acid, and getting more green veggies into their diets.

9. Congested Liver

 To put it mildly, we’re exposed to a lot of toxins each day. These come from the air we breathe, the foods we eat, the products we apply to our skin and those we use in our homes…and more.

And your liver is responsible for filtering out these harmful toxins and preventing a buildup of them within the body. This leads to one tired and congested liver, which can drain your energy.

To help support the liver, I like to recommend a supplement called N-Acetyl-Cysteine. I’ve found liver support to be so important in helping my clients recover from Hashimoto’s that I’ve dedicated an entire protocol to it in my new book, Hashimoto’s Protocol. If you find that taking N-Acetyl-Cysteine improves how you feel, you could benefit from following the full liver support protocol.

Of course, reducing your exposure to toxins is crucial for overall health.

You can test many liver functions with proper blood work.  Your liver might be congested even with normal lab results, but it's something to check nonetheless.

10. Adrenal Fatigue

In addition to liver support, focused attention on the adrenal glands can make a profound difference in energy levels. The adrenals produce several hormones important to wakefulness, stress tolerance, memory, anti-aging, and sex drive. When they stop producing enough of these hormones, which include cortisol, estrogen, and progesterone, adrenal dysfunction or fatigue develops.

When your adrenals are dragging, the first thing you want to do is reach for caffeine…and more caffeine…and then more, until it seems that reliable jolt just simply stops working. A possible explanation for this unresolvable exhaustion, among other symptoms such as frequent feelings of dehydration, cravings for salty foods, menstrual irregularities, and more, is adrenal fatigue.

Full recovery of adrenal function is possible, but it requires a strategic approach that includes rest, de-stressing, balancing blood sugar, reducing inflammation, and replenishing nutrients and adaptogens. All of these are incorporated into my Adrenal Recovery Protocol, which I’ve shared publicly for the first time (earlier versions have been used in my workshops) in Hashimoto's Protocol: A 90-Day Plan for Reversing Thyroid Symptoms and Getting Your Life Back

You can test for adrenal fatigue with a saliva test (blood tests can check hormone levels to also give clues). But you don’t have to wait for a diagnosis to start implementing one of the most important strategies in adrenal recovery–minimizing stress. Do this by starting to include more things that make you feel better each day and less that make you feel worse.

Maybe create more time with loved ones or give yourself the gift of a little extra sleep. My clients have also reported that being in nature, walking, or getting a massage can create feelings of calm.

In the worse column, it’s common to see examples such as being around toxic people, lack of sunshine or sleep, or fighting with love ones.


I know what it’s like to feel drained of all your energy and motivation.

I hope addressing these causes of fatigue will help you as much as it’s helped me and many of my clients. Let me know what works and what doesn’t–I look forward to hearing from you!

Do you struggle with fatigue?
Or have you dealt with it successfully? What has helped?


Izabella Wentz, the Thyroid PharmacistAbout Dr. Izabella Wentz

Izabella Wentz, PharmD, FASCP is an internationally acclaimed thyroid specialist and licensed pharmacist. She dedicated her career to addressing the root causes of autoimmune thyroid disease after being diagnosed with Hashimoto’s Thyroiditis in 2009.

Dr. Wentz is the author of the New York Times best-selling patient guide Hashimoto’s Thyroiditis: Lifestyle Interventions for Finding and Treating the Root Cause and the new protocol-based #1 New York Times bestseller Hashimoto’s Protocol: A 90-Day Plan for Reversing Thyroid Symptoms and Getting Your Life Back.

As a patient advocate, researcher, clinician and educator, Dr. Wentz is committed to raising awareness on how to overcome autoimmune thyroid disease through The Thyroid Secret Documentary Series, the Hashimoto’s Institute Practitioner Training, and her international consulting and speaking services offered to both patients and healthcare professionals. www.thyroidpharmacist.com 


These comments do not necessarily reflect the opinions of Whole New Mom, LLC.


    Speak Your Mind


  1. What brand or form of methylfolate do you recommend?

    • I personally have been using Pure Encapsulations. I try to buy supplements with as few additives as possible. My son doesn’t seem to tolerate methylfolate well so we’re using veggies for him and will likely lean on vegetable powders as well.

  2. An often overlooked cause of fatigue is hemochromatosis- iron overoad.

  3. As I look at the difference between hyper/hypo thyroidism, I discovered that you can actually be BOTH at the same time. Since I have many from EACH set of symptoms, I assume I have the both issue. Not sure how to approach this issue and get better, but still doing research. Thank you for this article, it will be another one I look to to find my answers. I do not feel confident going to doctors as all they want to do is put you on synthetic thyroid, and not really look into WHAT the real issue is, so I just plod along trying to do it myself.

    • Yes, you can. In fact, I had symptoms of both. However, I think what it is, is your thyroid is really one, but it can have episodes of the other, depending on the stimulus. For me, I am hypo, but certain things like eggs and other things would throw me into a hyper state. Once I removed those things and did other work, the hyper episodes lessened and even vanished. I haven’t been on any thyroid meds at all since my Hashimoto’s diagnosis. I’m way overdue for my next set of labs, but perhaps this will encourage you. https://wholenewmom.com/health-concerns/thyroid-disease-hashimotos-blood-test/

      I HIGHLY recommend Izabella’s books. I am doing more things and hope to share more, but they are a fabulous place to start. Blessings.