5 common causes of fatigue and what to do about them

Nutrient Deficiencies

Most everyone thinks of iron-deficiency anemia when thinking of fatigue, but lack of vitamin B12 and folate can be linked to megaloblastic anemia, a red blood cell defect that can lead to an undersupply of oxygen.  And indeed all the B vitamins (B1, B2, B3, B5 and B6) play a role in energy production in the body. 

Vitamin D and Vitamin C are also important for energy production as is magnesium, which is used in over 600 reactions in your body.  All of these are commonly deficient in the population at large. Vitamin D deficiency can be 36% of a healthy young adult population and as much as 57% deficient in inpatient populations. (1) Vitamin C was shown to be sub-optimal or deficient in 47% in young Canadian adults. (2)  Magnesium deficiency has been found in 84% of postmenopausal women with osteoporosis. (3)

A whole varied diet of nutrient dense foods and good digestion are key here as well as ruling out any other causes of these issues (such as blood loss or low stomach acid). 

Blood sugar imbalance

Trying to keep your energy up by eating a sugary snack or drinking a caffeinated drink such as tea or coffee, will ultimately have the opposite effect. What happens is you get a surge of blood sugar to give you some energy, but the body doesn’t like blood sugar to be out of a narrow range – too high or too low is seen as bad.  So you then get a flood of insulin to bring that excess blood sugar down as quickly as it can (and storing it as fat, by the way) and may even overcompensate in its zealous attempt to balance out your blood sugar, causing you to have a blood sugar crash.  What then follows is perhaps a cortisol surge, hunger, jitters and irritability.  You might then just grab some more food in order to make yourself feel better.

Ideally, we are eating for a steady level of blood sugar. It’s what you hear all the time: good quality protein, healthy fats, whole grains and lots of veg.  Avoiding sugar and starchy carbs and I was also go so far as to say as keeping your fruit intake to 2-3 servings per day. 


This one seems obvious doesn’t it?  We all know that if we don’t sleep well enough or long enough we don’t feel energetic. So sleep needs to be a priority.  And good sleep hygiene is critical. 

What does that mean? 

  • Going to bed on a set schedule as best you can (even if you are a shift worker, you will have some kind of schedule) – going to bed and rising at the same time each day.
  • Aiming for 7-9 hours of uninterrupted sleep.
  • Reducing stimulants before bedtime – that can be from caffeine and sugar to blue light from your phone or laptop screen. 
  • Making the room cool and dark.

If you are having trouble falling asleep and/or staying asleep, we might need to look at the next one:


Stress can obviously impact sleep, as cortisol released during the stress response works against melatonin, the sleep hormone. Also it can affect blood sugar balance, as discussed above.  And on top of all that, cortisol, the stress hormone, can also slow the thyroid gland down.

Short term surges of cortisol can make you feel energetic and ready to act, however over the long term the adaptive response of the body is to reduce cortisol production thus leading to a fatigue situation.

Techniques for managing stress can be as varied as the causes of stress – the short answer is – do what (healthy option) works for you – light exercise, breathing exercises, meditation, prayer, talk or CBT therapy.  Self care is key too – do nice things for you. Again this depends on your preferences: massage, a film, reading a good book, a manicure.


The thyroid gland is a small butterfly shaped gland in your neck just in front of your windpipe. It produces 2 forms of thyroid hormone, thyroxine (T4) and triiodothyronine (T3), the active form of thyroid hormone.  These control your metabolic rate at a cellular level.  If your thyroid function is low – that is, producing too little of these hormones – then you may experience intolerance to cold, weight gain, depression, poor concentration as well as fatigue.

I was once told by an endocrinologist that the thyroid gland is a “whacky little gland”, meaning that it responds up and down to different things.  It is not uncommon for stress to cause the thyroid gland to be temporarily underactive, but remove the stress and the thyroid can recover.  I have experienced this myself.

Your doctor might test something called TSH (thyroid-stimulating hormone) which tells the thyroid gland to put out more T4 and T3.  If this number is high, then the thyroid gland is deemed to be low or underactive or hypo. T4 might also be tested.  However, there can be a variety of drivers in thyroid malfunction, and in functional medicine we like to do more a comprehensive test of TSH, T4, T3, antibodies (to see if there’s any kind of autoimmune issue going on) and perhaps even rT3 (reverse T3 – which is a form of T3 which has been inactivated). Iodine status might also be tested. While the traditional medical treatment is the same for any “version” of hypothyroid, nutritionally speaking, knowing where something is going wrong helps decide how to support the thyroid nutritionally on a personal basis.  Is iodine or other nutrients deficient therefore causing an issue producing T4? Is there a conversion issue from T4 to T3?  Is there an autoimmune issue?  


I see many of the above things in my practice with clients.  And we always work on an individual basis to dig into what’s going wrong and what to do to correct it – often multiple things are going on. You have to be willing to look at a variety of factors. 

I will say that if you’ve had unremitting fatigue for more than 3 months, then you should bring this up with your doctor in the first instance.  He/she will likely do some blood tests which may cover some of the things above and more important, rule out anything more sinister.

Private Functional Testing can be done for thyroid, nutritional status, adrenal / stress profiles


1. Holick MF. High prevalence of vitamin D inadequacy and implications for health. Mayo Clin Proc. 2006;81:353–73.

2. Cahill L, Corey PN, El-Sohemy A. Vitamin C deficiency in a population of young Canadian adults. Am J Epidemiol. 2009 Aug 15;170(4):464-71. doi: 10.1093/aje/kwp156. Epub 2009 Jul 13. PMID: 19596710.

3. DiNicolantonio JJ, O’Keefe JH, Wilson W. Subclinical magnesium deficiency: a principal driver of cardiovascular disease and a public health crisis. Open Heart. 2018 Jan 13;5(1):e000668. doi: 10.1136/openhrt-2017-000668. Erratum in: Open Heart. 2018 Apr 5;5(1):e000668corr1. PMID: 29387426; PMCID: PMC5786912.

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