Get your ferritin checked before you accept being tired

If you're tired in a way that sleep doesn't fix, the test you want is ferritin. Not "a blood test." Not "the usual panel." Ferritin, the number that tells you how much iron you've got in storage, and ideally a CBC alongside it so you can see both halves of the picture.

This matters because iron deficiency shows up long before anemia does. You can walk into an office, get a complete blood count, be told your hemoglobin is fine, and walk out still deficient. The storage tank is nearly empty. Your body is just doing a heroic job of protecting the last of it for your red blood cells, which is exactly why the CBC looks reassuring while you feel like you're hauling a backpack full of wet sand.

The symptoms don't announce themselves as iron. They show up as being winded carrying a laundry basket to the second floor. Hair in the shower drain. Cold hands in a warm room. Restless legs at night. Headaches. Workouts that used to be easy and now take three days to recover from. And the strange one that's almost diagnostic on its own: a craving to chew ice. If you're crunching through a cup of ice every afternoon, ask for the test.

The numbers, and why "normal" isn't the same as "fine"

A CBC gives you hemoglobin, hematocrit, and MCV, which is the average size of your red blood cells. Iron-deficiency anemia tends to make cells small, so a low MCV is a clue. But it's a late clue.

Ferritin is the early one. And here's the frustrating part nobody tells you before you look at your own results: lab reference ranges for ferritin often start somewhere around 10 to 15 ng/mL at the bottom end, which means you can come back "within range" at 12 and be genuinely low on iron. Plenty of clinicians treat symptomatic women well above that floor, and many use a threshold closer to 30 ng/mL when deciding whether iron is worth addressing. Ranges vary by lab and by patient, so this is a conversation to have with your doctor rather than a verdict you hand yourself. But you should know that "not flagged" and "not deficient" are two different sentences.

One wrinkle worth asking about. Ferritin rises with inflammation, infection, and liver issues, so a single ferritin drawn while you're fighting something can read falsely comfortable. That's why doctors sometimes add a CRP, or look at iron saturation and transferrin, to see whether the number is telling the truth.

Where it's going

Iron deficiency isn't a personality trait or a life stage. It's an accounting problem. You're either losing iron faster than you take it in, or you're not absorbing what you eat.

For women of reproductive age, the biggest single source of loss is monthly bleeding, and pregnancy pulls hard on stores too. Frequent blood donation drains them faster than most donors realize. Endurance training adds its own quiet losses. A mostly plant-based diet gives you non-heme iron, which your gut absorbs less efficiently than the iron in beef or liver, so the intake side of the ledger is thinner than the food labels suggest.

Absorption problems have their own list: celiac disease, H. pylori, past bariatric surgery, and long-term acid-reducing medication, since iron needs stomach acid to be absorbed well. If you've been on a proton pump inhibitor for years and you're low on iron, those two facts are probably related.

And the one that isn't optional. If you're post-menopausal, or you're a man reading this over your wife's shoulder, unexplained iron deficiency needs a look at the gastrointestinal tract. Slow blood loss from the gut is a common cause, and some of the causes are serious and highly treatable when found early. Iron pills without a cause found is half a job.

Taking iron so it actually works

Most oral iron in the U.S. is ferrous sulfate, usually the 325 mg tablet, which contains about 65 mg of elemental iron. Read the elemental number on any bottle you pick up, because the big number on the front is the salt, not the iron.

Your doctor sets the dose. What you can control is everything around it, and it makes a real difference:

• Take it with vitamin C. A glass of orange juice or a 250 mg tablet improves absorption.
• Keep coffee, tea, milk, and calcium supplements away from it. The tannins in tea and the calcium in dairy both cut absorption. Two hours of separation is a reasonable habit.
• Ask about every-other-day dosing. Taking a large dose of iron triggers a hormone called hepcidin that blocks absorption for the next day or so, which is why daily dosing can absorb less well than alternate-day dosing in some people. Many clinicians now prescribe it that way. It's worth raising.
• Don't take it with your thyroid medication or with antacids. Same absorption fight.

Now the annoying part, said out loud. Oral iron constipates a lot of people, and it can cause nausea and cramping if you take it on a truly empty stomach. Your stool will turn black. That's the iron, not blood, and it's expected. If one form makes you miserable, ask about switching. Ferrous gluconate and ferrous bisglycinate are generally easier on the stomach, and a smaller elemental dose you actually take beats a bigger one you quit in week two.

Rechecking, and the mistake everyone makes

Symptoms improve before the tank refills. You'll feel better in a few weeks and conclude you're done. You're not. Rebuilding stores takes months, and stopping at the point where hemoglobin normalizes leaves you with a ferritin low enough to slide right back.

Get a recheck of ferritin and CBC after roughly eight to twelve weeks, with the timing your doctor picks, and plan on continuing well past the point where you feel human again. Then find out what the plan is for the next year, because if the cause of the loss hasn't changed, neither has your future.

If oral iron isn't working after a fair trial, that's information, not failure. It usually means poor absorption or ongoing loss, and both deserve investigation. Intravenous iron exists, it's routine, and it's the right answer for some women, including those with real absorption problems or losses too heavy to outpace with pills.

What to say at the appointment

Be specific and be brief. "I've been exhausted for four months, I'm short of breath on stairs I used to run up, my hair is shedding, and I'd like ferritin, a CBC, and iron studies." Bring the symptoms with numbers attached. Ask for the actual values, not "normal," and keep them so next year's draw has something to be compared against.

Then take the result seriously in both directions. If your iron is fine, good. That's not a dead end, it's a crossed-off cause, and thyroid function, sleep apnea, and B12 are all sitting right behind it in the line.

Being tired isn't a character flaw you've developed in your thirties. It's a finding. Go get the number.

This is general health education, not medical advice for you specifically. Talk to your doctor before starting iron, and don't supplement iron blindly, because iron overload is its own problem.