07/01/2026
You're so tired you can barely get through the day, have brain fog, maybe losing more hair than you'd like to admit, but taking iron supplements isn't getting you anywhere, and your thyroid meds feel like they’re not working. This may be why:
Your thyroid needs iron to convert T4 (the inactive thyroid hormone) into T3 (the active form your cells can actually use). So low iron means low conversion. Even if your TSH looks fine and you're producing T4, it might not be getting where it needs to go.
But here's where it gets interesting. Low iron usually isn't because you're not eating enough iron-rich foods or taking enough in supplements. A lot of the time, the real problem is that you're not absorbing what you take in, because your stomach acid is low.
Stomach acid is what breaks down the proteins and minerals in your food well enough for your small intestine to absorb them. When stomach acid is low, iron absorption drops. Zinc absorption drops too, and zinc is required for stomach acid production in the first place!
So, you end up with less zinc, which means less stomach acid, which means less iron absorption, which means less thyroid conversion, which means more fatigue, more brain fog, more of everything you've been trying to fix.
Round and round, getting worse and worse. It's like being on the worst merry-go-round ever.
Then there's the gut connection that ties it all together. Chronic low stomach acid creates an environment where dysbiosis (an imbalance of gut bacteria) can take hold. A disrupted gut microbiome contributes to intestinal permeability, also called leaky gut. And a leaky gut drives inflammation, which further impairs thyroid conversion and can trigger the immune response that leads to Hashimoto's. This also creates inflammation throughout your body, raising a hormone called hepcidin, which further decreases iron absorption and locks away the iron your body recycles form old red blood cells so you can’t use it.
Gut issues also set you up for histamine intolerance. Your gut can start being overpopulated with bacteria that produce histamine, and inflammation can also increase histamine production and lower the amount of enzymes produced that can clear it out. This causes a variety of symptoms often mistaken for low iron or thyroid dysfunction, since many overlap.
I’m talking weird anxiety that feels like it’s not from your brain but your body, air hunger, like you can’t get a satisfying breath in, and bone crushing fatigue.
So, when someone asks, "will I feel better when my ferritin comes up?" my honest answer is maybe, but only if we also figure out why it was low in the first place, and even if that was the sole reason for your symptoms!
There are a lot of clues in your basic bloodwork that can point to this. Finding those patterns is my favorite thing to do. ✳️ For more info on booking a bloodwork review, comment IRON.
