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What's Causing Your Fatigue? Ten Reasons You're Tired and How to Get Your Energy Back

Fatigue. You know that horrible feeling like you're constantly dragging - almost as if you're fighting to make it through the day, or past your next ___fill in the blank___?

The good news is this: our bodies are not betraying us. Instead, fatigue is a warning sign and a mechanism that keeps us safe. It might be a signal that you're putting your body through more than it can handle (knowingly or unknowingly), and it's slowing you down so you can continue to survive.

Your job? Listen to it.​​

And then, consider what you can do to help your body out! Here are our top 10 reasons why you might be so darn tired and what you can do about it. See what resonates with you, and take baby steps with our suggestions to toward feeling like your awesome, full-of-energy self again.

1. Dehydration

Yes. Sometimes it's that easy. Some estimations have found that up to 75% of us are not drinking enough water. When you're dehydrated, your blood is thicker, making it more difficult to distribute nutrients and oxygen throughout your body. You can do a quick test for dehydration by pinching up the skin on your knuckles or the back of your hand. If it takes longer than a couple of seconds to spring back, you might be dehydrated.


  • Track your water intake for a few days and get a gauge of how well you're hydrating. Shoot for half of your body weight in ounces.

  • Water is preferred, but if you can't stand plain water, try adding a squeeze of lemon or infuse with fruit. Or, try sparkling water.

  • Try to avoid dehydrating/diuretic beverages like coffee or high-sugar fruit juices that can actually contribute to dehydration; these don't count toward your daily hydration goal.

2. Vitamin D Deficiency

Vitamin D is a critical nutrient for generating energy and helping with calcium -- and in fact, it's not a vitamin at all, but a hormone. Your body can make some of its own, but several studies are showing now that sunlight alone, especially when you live in areas that aren't sunny year-round, is not enough. The journal Medicine notes that vitamin D deficiency is commonly found in patients experiencing fatigue; raising vitamin D to sufficient levels significantly reduced symptoms of fatigue. In addition, Vitamin D has shown great results in treating depression.

Don't blindly trust a high/low flag on a lab test to tell you if you're deficient: You could still be deficient, even if your doctor or lab result indicates you're normal. Why? Reference ranges you get from conventional labs indicate illness, like rickets, in the case of Vitamin D. On the flip side, functional ranges tend to be higher because this is the window in which someone feels healthy and well - not just "not-sick." References ranges for Vitamin D are generally around 30 ng/mL, but the Vitamin D council recommends a minimum of 40 ng/mL. Many functional medicine practitioners will aim for a window between 50-80 ng/mL. Over 100 ng/mL starts getting into overdose territory where fatigue and symptoms like stomach cramping and nausea can occur.

Also, you might be burning through vitamin D faster than usual if your immune system is over-activated (like if you're fighting a cold or virus).


  • Ask your doctor to check your Vitamin D levels (specifically the 25(OH)D test, not the 1,25(OH)₂D test) and supplement accordingly to raise up to a maintenance level.

  • Consider working with your doctor to determine why your levels may be low to begin with.

  • And get some sun!

  • Check out our guide on Vitamin D for more info and tips.

3. Nutrient deficiency

There are other nutrients that are important for energy, like B12 and iron/ferritin. Sometimes, all it takes is replenishing your stores and investigating why so you can prevent recurrence.

If you're severely low in either of these nutrients, you may even discover anemia - the condition in which your red blood cell count is too low. When you have too few red blood cells, you'll notice that you get winded much easier, or your endurance is less than it used to be. Anemia can be caused by low B12 or iron. Pernicious anemia is an autoimmune condition in which your immune system is destroying your ability to absorb and use B12. Anemia happens most often in women due to menstruation and loss of additional iron through blood.

Other important nutrients that could be contributing to fatigue include: Vitamin C, magnesium, sodium, L-tryptophan, L-carnitine, coenzyme Q10, and essential fatty acids.


  • Talk to your doctor about testing your nutrient levels, particularly B12 and Iron/Ferritin.

  • Be careful not to blindly supplement, as overdosing on some of these can have disastrous effects!

  • Support digestion with digestive enzymes to break down food & get more nutrients from the food you're eating.

4. Adrenal Dysfunction or Stressed Adrenals

Between the thyroid and adrenals, these two glands control virtually every aspect of our metabolism, including energy production and storage. The adrenals pump out cortisol to help keep us alive, and it's cortisol's job to regulate our circadian rhythm, fat storage, and also prioritize other body functions. When your body is under stress, cortisol is dispatched to come to your rescue. Over time, if you're constantly stressed & sending out massive amounts of inflammatory cortisol to boot, your brain (the hypothalamus) will turn down the volume on cortisol to protect your body from further damage. That's when the tiredness sets in because you simply can't any longer.

Stressors aren't just emotional. They can include: blood sugar dysregulation, over-exercise, high toxic burden, and perceived mental stress (like that presentation you had to give for a group of 50 people at work).

Do you have adrenal dysfunction? Symptoms vary, but at the point of fatigue, you'll notice a drop in endurance and maybe experience being tired-but-wired. You might also notice elevated (LDL) cholesterol and hold most of your weight around your mid-section.


  • You can test for adrenal dysfunction with a saliva collection test.

  • Support the adrenals with herbal supplements called adaptogens, and feed them plenty of vitamin C.

  • Check out our blog post for more strategies to heal the adrenals & reverse your fatigue.

  • Also, get at least 8 hours of sleep per day -- in experiments, scientists generally use sleep deprivation as the fastest way to induce adrenal dysfunction in lab rats.

5. Low Thyroid Function

The thyroid is the other thermometer for the body and it has the power to turn down all of our metabolic processes, including energy production, when our bodies are in survival mode. There are several root causes for low thyroid function, including: toxicity, food intolerances, nutrient depletions, stress (physical or mental), and more. When we're under stress, our bodies can also produce a hormone called Reverse T3, which is a look-alike for active thyroid hormone, but it's like a key that fits in the door but doesn't turn the deadbolt lock. We feel tired as a result because RT3 is blocking usable thyroid hormones.

If you've been diagnosed with hypothyroidism,