When you’re struggling to sleep or suffering from sleepiness during the day, many factors could be at play. You may be drinking too much caffeine or staying up too late. Or perhaps you have a medical condition or sleep disorder that’s causing this extreme tiredness (fatigue).

To find out the cause of your sleep problems, you may need many tests. These may confirm or rule out various health conditions and other problems.

Hematocrit and hemoglobin test

You may need a hematocrit/hemoglobin blood test to measure the levels of these substances in your blood. If you have low hematocrit and/or hemoglobin, this means you have anemia. This is a blood disorder that can cause you to be tired and sleepy during the day. It can also lead to restless legs syndrome. Abnormal levels of hemoglobin may also mean you have an iron deficiency, chronic illness, or lung disease. All of these can contribute to sleep problems.

Arterial blood gases test

An arterial blood gas test measures the levels of gases, including oxygen, and carbon dioxide, in the blood. The test is done by drawing blood from an artery in the wrist. This takes only a few minutes. The test can diagnose or rule out many conditions, including problems with breathing. Trouble breathing, shortness of breath, and sleep apnea are breathing issues that can affect sleep.

Thyroid function test

Thyroid function can be looked at by checking the levels of thyroid hormones in the blood. These hormones help regulate the body’s metabolic processes. A thyroid function test may signal an underactive thyroid gland. This is called hypothyroidism and it may cause fatigue and lethargy. Or it may show an overactive thyroid, a condition called hyperthyroidism. This can cause insomnia or fatigue. Either of these conditions can play a part in sleep problems.

Drug and alcohol toxicology screening

A test to check for drugs and alcohol in the blood can help find out if drugs or alcohol are the cause of sleep disorders, such as insomnia. People may use drugs or alcohol as sleep aids. But doing so can backfire. For instance, a glass of wine before bed can lead to drowsiness, so falling asleep is easy. But the alcohol can then cause middle-of-the-night wakefulness, resulting in insufficient sleep. You may give a blood or pee (urine) sample in either a healthcare provider’s office or a lab.

Epworth sleepiness score

This test is a questionnaire that helps assess how sleepy you are during the day. It also looks at how likely you are to fall asleep during daytime hours and during certain activities, such as watching TV or sitting in a car. Chronic daytime sleepiness may mean that you have a sleep disorder.

Beck depression index

This test asks questions to investigate for depression. The questions are about feelings of sadness, guilt, self-criticism, fatigue, sleep problems, and other symptoms that often signal depression. Depression and some of the medicine used to treat it are commonly linked to insomnia and other sleep disorders.

Electrooculogram

In sleep medicine, the EOG (electrooculogram) is used to find different types of eye movements during sleep. Electrodes that measure electrical signals based on eye movements are placed on the sides of the eyes. These lets the healthcare provider identify different stages of sleep, particularly rapid eye movement (REM) sleep. It’s used as part of the polysomnogram.

Chin and leg electromyogram

The electromyogram test, or EMG, measures the electrical activity of the nerves in the chin and the legs. It’s often done in a sleep clinic during a sleep study. It involves attaching electrodes to the skin on the legs and chin to look at the activity of the muscles. The recorded nerve activity can show increased activity of muscles during sleep, which can help diagnose sleep disorders.

Polysomnogram

A polysomnography test may be done to check the patterns of brain waves and other physical functions during sleep. The test is often done in a sleep clinic overnight to look at the body’s activity during sleep. The test measures heart rate, respiration, muscle activity, blood pressure, brain activity, and eye movement. The test can show whether you are asleep and whether you have any problems in the sleep pattern. This test often includes an electroencephalogram (EEG), EOG, and EMG. The EEG measures brain activity.

Actigraphy

Actigraphy measures rest and activity cycles. It uses a wristwatch-type sensor that measures your body movements day and night over 1 to 2 weeks.