Adrenal or thyroid? Tests for tiredness and what each can show

If you are tired and trying to work out whether it is your thyroid or your adrenal glands, the honest first step is to widen the question. Both glands can cause tiredness, but so can low iron, poor sleep, depression, diabetes and many other things. No symptom on its own tells an adrenal problem from a thyroid problem, which is why blood tests come into it.

This page compares what the two glands do, how their symptoms overlap, and which test answers which question.

TSH

One blood test that is a common first check of the thyroid.

$39

A TSH test looks at the thyroid. It does not test the adrenal glands. Follow the instructions on your lab order.

See this test at HealthLabs

Price checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

Adrenal or thyroid: what each gland does

The thyroid is a small gland at the front of the neck. MedlinePlus says its hormones control how your body uses energy and affect nearly every organ, from heart rate to digestion. Too little thyroid hormone slows body functions, and too much speeds them up.

The adrenal glands sit above the kidneys and make cortisol. MedlinePlus says cortisol affects almost every organ and tissue and helps with your response to stress, inflammation, blood sugar and blood pressure.

One gland in the brain, the pituitary, controls both. It makes TSH, which tells the thyroid how much hormone to make, and ACTH, which tells the adrenal glands how much cortisol to make. See the ACTH blood test for the adrenal side of that chain.

How the symptoms overlap

The lists below come from MedlinePlus and NIDDK. Nobody has every symptom, and many people have only one or two.

	Underactive thyroid	Overactive thyroid	Low cortisol (adrenal insufficiency)
Energy	Fatigue	Fatigue	Long-lasting fatigue, muscle weakness
Weight	Weight gain	Weight loss, even when eating more	Weight loss, with loss of appetite
Mood and sleep	Depression	Nervousness, irritability, trouble sleeping	Irritability and depression
Gut	Constipation	Frequent bowel movements or diarrhea	Nausea, vomiting, diarrhea, belly pain
Heart and blood pressure	Slowed heart rate	Rapid or irregular heartbeat	Low blood pressure that drops further on standing, with dizziness or fainting
Skin and temperature	Dry skin, sensitivity to cold	Sweating, sensitivity to heat	Darkening of the skin in Addison’s disease
Other pointers	Dry, thinning hair; joint and muscle pain	Shaky hands; an enlarged thyroid (goiter)	Salt cravings, low blood sugar

Tiredness is on every list, which is the problem. NIDDK says that for hypothyroidism, symptoms such as fatigue and weight gain are common and do not necessarily mean a thyroid problem. For adrenal insufficiency, NIDDK says symptoms come on slowly and may be overlooked or confused with other illnesses.

A small hospital series from Poland shows the confusion in practice. Among 60 people with primary adrenal insufficiency, the wrong diagnoses made before the right one included hypothyroidism, depression and chronic fatigue syndrome (Int J Endocrinol, 2013). In the same series, 26 people (43 percent) had thyroid antibodies, and 11 of them already had hypothyroidism treated with thyroxine, so the two problems can sit side by side. A series of 60 people from one centre in Warsaw can’t tell you how often that happens in general.

Which test answers which question

Your question	Test	What it can and can’t tell you
Is my thyroid underactive or overactive?	TSH, sometimes with other thyroid markers	MedlinePlus says TSH shows how well the thyroid is working but can’t show the cause. An unusual result usually leads to T4, T3 and antibody tests.
Could low iron explain this?	Ferritin	MedlinePlus says it shows how much iron you have stored. Symptoms of low iron include weakness, fatigue and dizziness. Inflammation can raise ferritin.
Is something off with blood sugar, kidneys, liver or electrolytes?	A metabolic panel (BMP or CMP)	MedlinePlus lists fatigue among the reasons to order a CMP. See sodium, potassium and cortisol.
Is my cortisol low?	Blood cortisol, often with ACTH, then usually an ACTH stimulation test	NIDDK says the ACTH stimulation test is the one used most often to diagnose adrenal insufficiency. A single cortisol can’t diagnose or rule it out.

The seller’s page says the TSH test needs no fasting, and that a thyroid panel with TSH adds other thyroid markers. Check the exact markers on the order before you buy. Two more tests that fit this question are listed here.

• FerritinStored iron, a common thing to check when you feel tired $29 See this test at HealthLabs
• CortisolOne blood draw. One result can't diagnose or rule out an adrenal condition $109 See this test at HealthLabs

Sold by HealthLabs. Prices checked November 2026. Not available in ND, RI, NY, NJ, MD and HI. We earn a commission on sales.

For a fuller look at how timing changes a cortisol result, see the cortisol test guide. For the thyroid side, our page on cortisol and the thyroid covers how the two systems relate.

When the adrenal question is worth asking

NIDDK says the most common cause of adrenal insufficiency overall is suddenly stopping corticosteroid medicine after taking it for a long time. It also lists autoimmune disease, some infections, pituitary problems and head injury among the causes. Signs that make an adrenal cause more likely than plain tiredness include:

• Weight loss and loss of appetite you can’t explain.
• Dizziness or fainting when you stand up.
• Craving salty foods.
• Darkening of the skin, most visible on scars, skin folds and the lips.

If you have these, or you take a steroid medicine and feel unwell, talk to a clinician. Don’t stop or change a steroid medicine yourself. Low cortisol explains the work-up.

Call 911 or seek urgent care instead of ordering a test if you have vomiting you can’t stop together with severe weakness, or fainting. See adrenal crisis.

Where “adrenal fatigue” fits

Wellness sites often suggest that stress wears out the adrenal glands and a salivary cortisol profile can show it. A 2024 paper in the Journal of the Endocrine Society says adrenal fatigue has never been scientifically proven to exist, that those profiles have never been validated, and that accepted tests (serum cortisol, ACTH and the ACTH stimulation test) are usually normal in people given the label. That is why the sensible checks for tiredness are the ones above. See adrenal fatigue for the evidence.

What to bring to a clinician

MedlinePlus says that if tiredness lasts several weeks, your provider will ask about your sleep, daily activities, appetite and exercise, do a physical exam and likely order lab tests. It helps to bring:

• How long you have felt this way, and what has changed.
• Every medicine and supplement you take, including steroids.
• Whether your periods are heavy or irregular.
• Any weight change, dizziness or digestive symptoms.

Blood tests are one part of that visit. They do not replace it.

Questions people ask

Can a thyroid problem look like an adrenal problem?

Yes, in the sense that the symptoms overlap. Fatigue, weight change, low mood and digestive upset appear in both. Only testing, and the rest of your history, separates them.

Do the thyroid and adrenal glands work together?

Both are controlled by the pituitary gland, which sends TSH to the thyroid and ACTH to the adrenal glands. They are separate glands with separate hormones, and a result for one says nothing about the other.

Should I test cortisol or thyroid first?

MedlinePlus doesn’t rank them. It says a provider looks into long-lasting tiredness through questions, an exam and lab tests. Thyroid and iron checks fit plain tiredness. Weight loss with poor appetite, dizziness on standing, salt cravings or darkening skin point toward the adrenal glands, and cortisol testing fits those signs. A clinician can tell you which applies to you.

Keep reading

• Adrenal fatigue

  What the evidence says about a label that is not a recognized diagnosis.

• Low cortisol

  Causes, emergency signs and how adrenal insufficiency is tested.

• Cortisol and the thyroid

  How the two hormone systems relate.

• All adrenal and related tests

  ACTH, DHEA-S, aldosterone and more, with what each shows.