Feeling Tired All the Time? 7 Hidden Health Causes Your Primary Care Doctor Can Check

September 17, 2026

Medically Reviewed ByDr. Sanjay Murthy, MPHTM, DABAM, DABUCM, BC-ADM, CGCP, CWHS

Everyone has a rough week now and then, but if you've felt drained for a month or more — the kind of tired that a good night's sleep doesn't fix — it's worth asking whether something medical is behind it. Chronic fatigue has a long list of possible causes, and several of the most common ones show up on routine bloodwork that many patients haven't had checked in years. Here are seven worth ruling out.

An underactive thyroid, or hypothyroidism, can leave you tired, cold, and foggy for months before anyone thinks to check it — a simple blood test called TSH usually catches it.

Iron-deficiency anemia is especially common in women with heavy periods and in anyone with a diet low in iron-rich foods, and it shows up clearly on a complete blood count.

Low vitamin B12 or vitamin D is common in Michigan, especially B12 in older adults and anyone on certain medications, and vitamin D in anyone who spends most of the winter indoors.

Sleep apnea is worth considering if you snore, wake up gasping, or still feel exhausted after eight hours in bed — your sleep may be interrupted dozens of times a night without you knowing it.

Undiagnosed or poorly controlled diabetes can cause persistent fatigue from both high and swinging blood sugar, often before any other symptom shows up.

Depression or anxiety is a genuinely medical cause of fatigue, not a personal failing, and it responds to treatment just like any of the other items on this list.

A medication side effect is easy to miss. Blood pressure medications, antihistamines, and several other common prescriptions can cause fatigue without anyone connecting the dots.

None of this requires guesswork on your end. At a visit, we'll start with a conversation about your sleep, diet, stress, and medications, then order bloodwork targeted at the most likely causes rather than ordering everything at once. Most people get an answer, and a plan, from one visit and one round of labs.