All Women's Talk

7 Blood Tests for Fatigue to Have Your Doctor do if You're Always Tired ...

By Chelsie

If you have been feeling more tired than usual you might want to consider asking your doctor to run certain blood tests for fatigue. Your tiredness could be an indicator that something is wrong. A few years ago, I became very tired and couldn’t explain why I felt so run down. Knowing thyroid problems run in my family, I went to my doctor and asked her to test my thyroid. The results showed I had severe hypothyroidism that was progressively getting worse every day. I was so glad I asked my doctor to run some blood tests for fatigue. If I hadn’t I would have gotten worse without knowing why. Instead, I received the proper treatment and slowly started feeling better.


The TSH test is one of several important thyroid blood tests for fatigue. TSH stands for thyroid stimulating hormone. This hormone is produced by the pituitary gland and is responsible for signaling the thyroid to produce a couple of hormones that are very important for your wellbeing; free T4 and free T3. If your thyroid gland is not producing enough of these important hormones, your pituitary gland will stimulate the production of more TSH to try and create balance. When this happens you will have fatigue, weight gain, dry skin, constipation, cold intolerance, hair loss, and menstrual irregularities. All of these symptoms are associated with hypothyroidism; the disease that made me feel like I was walking around with bricks on my feet. In addition to TSH, you will also want to have your doctor check your free T4 and free T3 levels since these hormones drop in a person with hypothyroidism.

2 Free T4

One of the important hormones that is produced by the thyroid gland is thyroxin, or T4. This hormone makes up 90% of your thyroid hormones. T4 can be bound to protein or unbound. The unbound T4 is called free T4, and this is the most important measure of T4 to have checked because it is the most biologically active. Hypothyroidism occurs when your thyroid doesn’t produce enough free T4. Without enough of this hormone you can feel very fatigued and very sick.

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3 Free T3

Free T3 is another hormone that is produced by the thyroid; however, not very much free T3 is made by the thyroid gland. A large portion of it is made when the body converts free T4 into free T3. Free T3 is actually the most biologically active thyroid hormone, as it is taken in by tissues throughout the body. Not everyone who has hypothyroidism will have low levels of free T3. I, however, did experience low levels of free T3, and I can tell you that when the free T3 hormone is low you really feel crummy. I hardly had enough energy to get myself out of bed.

4 Cortisol

Hypothyroidism is not the only disease that can cause fatigue; there are many others, including adrenal insufficiency. Adrenal insufficiency can make you feel very tired, and it occurs when the adrenal glands don’t produce enough cortisol. Cortisol is a hormone that metabolizes proteins, lipids, and carbohydrates. It also affects blood glucose, helps maintain blood pressure, and regulates the immune system. Cortisol levels change throughout the day, with the highest level being in the morning. Doctors will often order several tests throughout the day in order to establish a daily pattern. Cortisol levels can be checked in blood, urine, and saliva. So, if blood tests aren’t your thing there are other options.

5 Hemoglobin A1C

Hemoglobin A1C, HA1C for short, is a measurement of glucose overtime. This one test actually has the ability to provide a picture of the glucose levels in your blood over the last few months. This test is frequently used to diagnosis diabetes, which is actually a cause of fatigue. Along with fatigue, people with diabetes can also experience blurred vision, slow healing, and an increase in thirst and urination. This test has become a standard test doctors order during routine physicals, and it is very likely that you have already had yours checked.

6 Vitamin D

Vitamin D deficiency is actually very common, and although vitamin D is usually associated with bone health, a deficiency in it can cause fatigue. There are 2 types of Vitamin D present in blood, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D. 25-hydroxyvitamin D is the inactive precursor to the other form, and it is the form that is most often measured in blood tests. This is due to the fact that it is present in the blood for a longer amount of time. If your Vitamin D blood test shows a deficiency, follow your doctor’s orders and take your Vitamin D supplement. Your energy levels just might return to normal once you correct the deficiency.

7 Iron

I did not forget one of the most common tests doctors check when their patients come in complaining about fatigue - iron. Anemia is a problem that arises when a person does not have enough iron, and the hallmark symptom of anemia is fatigue. Iron is necessary for the production of red blood cells, which carry oxygen throughout the body. If you do not get enough iron in your diet, your body will draw upon iron it has stored in tissue, and eventually you will become anemic. There are several different tests doctors order to check for anemia. These include serum iron, serum ferritin, and total iron binding capacity. All three of these tests together provide a better picture of possible anemia.

Fatigue creeps up on everyone now and then, but if you are excessively tired you should consider seeing your doctor. Your doctor can order these blood tests to make sure nothing serious could be causing fatigue. However, if your blood tests are fine you may want to consider adding a few naps into your weekly routine. Have you been excessively tired lately?

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