I’ve been feeling really tired when I run. I’ve been meaning to write about this, and almost a full year later, this topic is becoming relevant again.Sometime last year I started the every day is run day streak, where I ran every single day of the year. Well, I tried to. I didn’t make it due to a RER injury, but did last all the way until the end of July. It didn’t come without some struggles and health challenges.

Disclaimer: what you’re about to read is my experience. I don’t recommend or encourage self-diagnosing and self-treating, so if you think you’re having a similar issue, go see a doctor!

During my run-every-day streak, I started heart rate training. Not in the classical sense of heart rate training, but according to this Maffetone Method that Ben described in our last post. In other words, we’re building endurance and strength by conditioning the “aerobic engine,” also known as the heart. Read: no runs over 80% of max heart rate. In doing so, it means the possibility of more miles because of lower intensity. I was easily running 40-, then 50-, then 70-, and 80-, (and even over 100!)-mile weeks and still feeling fresh!

Once I started consistently outrunning my previous lifetime maximum mileage PRs (anything over 50 miles), I started feeling really tired and run down. It was hard to get the energy to wake up and sit at my desk some days! Still, I assumed this was a nutrition issue. On advice from friends, I was clearly iron-deficient. I added iron supplements and started eating more red meat. I sucked down spinach like it was my job. I tried to get enough iron, but not iron poisoning!

I continued running, but as my high-iron weeks went on, I didn’t feel better and my 80% pace kept getting slower and slower. My mile times were getting slower (we had been doing mile time trials). An issue of too much mileage? I took a few lower-mileage weeks. One day, I tried running a time trial on the track and didn’t make it to a mile before I had to stop. I was really winded, I couldn’t catch my breath, and felt like I’d just completed a marathon (In reality, my watch indicated .7 miles). This was starting to become a trend– I couldn’t make it more than a half mile without feeling completely fatigued. My legs just couldn’t go. I felt so defeated.

Finally, I saw my friendly neighborhood doctor (a friend of ours!) and she recommended a blood test to get to the root of the problem. Eeek! 

Of course, it took forever and a half to fill up all of the SIX vials of blood (::shudder::). I didn’t look, either. I’m actually feeling a little sick to my stomach just thinking about this experience. ::shudder:: (again) Let’s move on.

Fast forward a few days…

Results? Surprises.

Iron levels? Just fine.

Just about everything else? Mostly fine. Except…

145 pg/ml might have put me into a possibly-ok range, but at 81 pg/ml, that’s still considered over 50% below normal levels by this guide.


See you that? It’s not low… it’s panic low.
My red blood cell, hemoglobin, and hematocrit levels were really low. Not being an expert of these (besides knowing that they all made me really TIRED!), I did some googling and thought I’d share these definitions from the Mayo Clinic:
Red blood cells, or erythrocytes (uh-RITH-ro-sites), transport oxygen throughout your body.
  • RBC: Red Blood Cell count.
  • HGB: Hemoglobin levels. Hemoglobin is a protein in your red blood cells that carries oxygen to your body’s organs and tissues and transports carbon dioxide from your organs and tissues back to your lungs.
  • HCT: Hematocrit. The proportion of your total blood volume that is composed of red blood cells. A hematocrit (Hct) test indicates whether you have too few or too many red blood cells — conditions that can occur as the result of certain diseases.
All of these things tied up vitamin B12 deficiency (pernicious) anemia with a bow! No wonder eating all that spinach never helped… there are several kinds of anemia, but iron deficiency anemia happens to be the most common and well-known.
In hindsight, I experienced a few of the symptoms of this particular type of anemia, affirmative in bold:
  • Fatigue
  • Shortness of breath
  • Dizziness
  • Pale or yellowish skin
  • Swollen tongue that may appear dark red
  • Weight loss
  • Diarrhea
  • Numbness or tingling in your hands and feet
  • Muscle weakness
  • Irritability
  • Unsteady movements
  • Mental confusion or forgetfulness
It’s interesting because I’m not sure how long I’ve been deficient  – it may be that I’ve had some degree of this (or symptoms) for a while and they didn’t become so apparent until I started running more. In the months leading up to the blood test, I started noticing that I’d black out/lose vision every time I stood up from sitting — I just dismissed it as my blood pressure being temporarily wonky, thinking nothing more of it. And I certainly don’t doubt forgetfulness/mental confusion has been an issue… haha, it always is.
Get more B12.
I was told to get some sub-lingual vitamin B12, 2500 mcg, and take it daily. (It’s the kind that melts under your tongue, not the pill version). As any dietitian will tell you, it’s better to get your vitamins from food, but my levels were so low we needed a jump-start with supplements. Turns out there are very few foods I eat that are on the list of foods containing the most B12! Recommended Daily Allowance (RDA) is 2.4 micrograms daily. [Ps- I won’t die with regret if I never catch, roast, and eat a squirrel.]

I was fortunate that the B12 supplements worked. If it wasn’t absorbed well enough or if my body couldn’t process it properly, the only other alternative would have been B12 shots. Yeah – shots! The horror!

Oh, and did you know? B12 is the active ingredient in a lot of energy drinks. It’s the ingredient that gets you feeling amped!! So if your B12 levels are normal and you ingest 2,500 micrograms, I’ve heard you’ll feel like you drank 3 cups of coffee. (Perhaps a way to get your caffeine-free energy boost? The internet said high doses of B12 are considered safe so it must be true.)

Red blood cells usually take 3 months to fully regenerate and replenish, so these supplements were the short-term treatment. Getting B12 in my food was a part of the long-term treatment plan. Things eventually got back to normal, and I felt better after 1 week, 2 weeks, a month, and better after 2 months, and 3 months later I was completely fine and feeling strong!

Like a total goof, I quit taking the B12 supplements, thinking that I was probably getting enough (I mean, I only need 2.4 micrograms a day!) by eating fortified cereal and occasionally seafood. I’m not sure if that’s the case, because – a full year later – I feel like I’m experiencing the same symptoms, all over again. Same shortness of breath, same extremely fatigued feeling. I’m really glad to catch it early this time around.

Back on the B12 train!
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