A Miserable Married Couple – B12 & Fatigue

Nutrient deficiencies can be one of the greatest contributors to fatigue – even if you’ve been to your doctor and ‘all your tests are normal’.

I routinely find at least one of these four nutrients as deficient in my fatigue patients:

  • Vitamin B12
  • Vitamin D
  • Magnesium
  • Iron

What I find interesting, though, is most fatigue sufferers are never checked for ALL of these nutrients. Sure, your doctor may check one or two of them, but all levels should be checked if you want to find the underlying cause of your fatigue.

I recommend every time you have blood work done, get a copy of the results for yourself. That way you’ll know your own numbers and can start tracking them from year to year. Then if a disparity arises, you may catch what a family doctor might overlook.

(Some patients are reluctant to do this. Don’t be! They’re your records, and you’re entitled to a copy for yourself! No one will care more about the meaning of your test results than you.)

Honestly, fatigue and low B12 go together like a miserable married couple.

Testing Vitamin B12

A simple blood test can determine your B12 levels.

The ‘normal’ range for B12 is 133-675 pg/ml.


The ideal B12 is above 600 pg/ml.

I rarely see this is in my practice, though.

Most fatigue patients are at 150-250. This is why you can be told ‘everything’s normal’ even though your B12 is clearly in the low end of the ‘normal’ range.

Most people do not get enough B12 in their diet, especially if they are not fans of fish and seafood (like me!). Here are the top 10 foods richest in vitamin B12:

  • Clams
  • Liver
  • Kidney
  • Beef
  • Lamb
  • Oysters
  • Mackerel
  • Crab
  • Herring
  • Organ meats

B12 is also made by the friendly bacteria, or probiotics, in your large intestine. So, if you have B12 deficiency it may be because you do not have enough probiotics in your colon.

Besides fatigue, symptoms of low B12 can also include:

  • weakness,
  • lightheadedness,
  • pale skin,
  • rapid breathing and heartbeat,
  • easy bleeding (including gums) or easy bruising,
  • sore tongue,
  • upset stomach,
  • unusual weight loss, and
  • diarrhea or constipation.

As for treatment, if you think you’re eating enough of B12-rich foods, then what it really comes down to is figuring out if the B12 is not getting absorbed properly, as with pernicious anemia or silent Celiac disease, and/or if it’s being used up faster than it should be, like with a hidden infection (parasite, yeast overgrowth, bacterial overgrowth).

Supplementation of B12 is best taken one of two ways: as a painful injection, or as a painless sublingual melt-under-the-tongue lozenge. Studies have compared them head to head, and the results show that the painless sublingual lozenge works just as well as the painful shots.

Besides fatigue, B12 is helpful for treating and/or preventing:

  • back pain,
  • muscle cramps,
  • migraines,
  • sciatica,
  • anxiety,
  • depression,
  • poor memory,
  • diabetes,
  • infertility,
  • and much more!

DO NOT underestimate the importance of proper B12 levels to maintain your health and avoid fatigue.

Insist that your doctor tests you once a year, especially if you suffer with fatigue!

And, find a good Functional Medicine doctor to help you get to the root cause of your fatigue.

Like I always say:

Find the cause.

Fix the cause.

Feel normal again!


Dr. Carri Drzyzga, DC, ND – The Functional Medicine Doc

Find the Cause. Fix the Cause. Feel Normal Again!

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