Can a blood test explain your sleep problems?

The question behind a bad night

Everyone sleeps badly sometimes. When the nights stay short week after week, when you wake at three and do not fall back asleep, most people start wondering whether something in the body is behind it. That is a reasonable question.

The answer is partly yes. A small number of conditions disturb sleep and can be measured in blood. They are worth knowing about, because they can be treated. They are also less common than the explanations no test reaches.

This article covers what a blood test can contribute when you sleep badly, and where the limit runs.

The thyroid

The thyroid sets the pace of your metabolism, and the two directions show up in sleep in different ways.

In hypertyreos (an overactive thyroid), 1177 describes the symptoms like this: you sweat and feel warm, you sleep badly and are often very tired, you have palpitations and a high pulse, and you lose weight even though you eat as usual. Poor sleep is explicitly part of that picture. 1177 also notes that the symptoms can come on slowly and be present for months or years before you notice anything.

In hypotyreos (an underactive thyroid), the picture differs. 1177 describes becoming more and more tired, feeling cold easily and low in mood, and later getting dry skin and dry hair, gaining weight and having a slow pulse. Disturbed sleep is not listed there. What is described is tiredness that sleeping does not clear. The distinction is worth holding on to when you try to put words to your own complaint.

The work-up starts with TSH. TSH is produced in the pituitary gland and prompts the thyroid to make the hormones thyroxine and triiodothyronine, and according to 1177 the test can show whether the thyroid is working as it should. High values usually reflect an underactive thyroid and low values usually an overactive one. In a work-up, thyroid hormone levels are measured together with TSH.

Iron and restless legs

Restless legs, known in Swedish also as Willis-Ekboms sjukdom (Willis-Ekbom disease), is described by 1177 as numbness, tingling or a crawling sensation in the legs when you have been still for a longer time. You can feel it at night when you lie in bed ready to sleep. Falling asleep is usually what suffers, which is why the problem belongs in an article about sleep.

1177 states that underlying causes can be järnbrist (iron deficiency), kidney failure, diabetes, a rheumatic disease or another illness. Iron deficiency comes first in that list, and it is the one an ordinary blood test picks up most directly.

Ferritin is the value used to judge your iron stores. Internetmedicin, the Swedish clinical reference for doctors, states that serum ferritin reflects the body's iron stores. There is one pitfall worth knowing: ferritin rises with inflammation, and internetmedicin notes that a normal ferritin can still be consistent with iron deficiency. Ferritin is therefore read alongside transferrin saturation and CRP rather than on its own.

If you have these sensations in your legs, 1177 says to contact a vårdcentral (primary care centre) when they are hard to relieve yourself. Iron treatment is a medical decision, not something you start off a result sheet.

Breathing pauses do not show in blood

Sleep apnoea, according to 1177, means short repeated pauses in breathing while you sleep, because the airway closes off, for example when the tongue falls back into the throat. The symptoms listed are being extra tired in the morning when you wake, being tired during the day, and snoring.

This is the common explanation a blood test can never give you. Night-time breathing pauses are measured by recording your breathing while you sleep.

1177 sets out the route. Contact a vårdcentral if you know that you snore and feel tired during the day. The doctor decides whether you need further examination, and you can then be given a remiss (referral) for a sleep investigation at a sleep laboratory. Measuring your breathing shows whether you have pauses while asleep. A polysomnography gives the doctor information about how you sleep across a night.

Treatment exists. 1177 describes CPAP, which blows a gentle stream of air into the throat through a mask so the airways stay open, and a mandibular advancement splint, which draws the lower jaw forward and stops the tongue falling back.

Most of it is not in the results

1177 sets out the causes of sleep difficulty, and the list runs long: noise in your surroundings, worry and anxiety, nightmares, breathing trouble, frequent trips to the toilet, hormonal complaints, alcohol, nicotine and caffeine, snoring and sleep apnoea, illnesses such as heart failure, stroke, dementia, Willis-Ekbom syndrome and Parkinson's disease, long-term pain, mental health problems including exhaustion disorder, depression, anxiety and post-traumatic stress, plus ADHD and autism.

Count how many of those a blood test measures. Thyroid function and iron status are in there indirectly. The rest of the list is not.

1177 describes sleep difficulty as taking at least 45 minutes to fall asleep in the evening, waking once or more during the night and struggling to fall back asleep, or waking too early in the morning before you have had enough sleep. For long-standing problems, cognitive behavioural therapy is the treatment recommended first. If the problem is tied to stress, 1177 says the important step is to address what is causing the stress.

1177 also names the point to seek help: when sleep problems do not improve despite the changes you have made to sleep better.

What a normal result gives you

A blood test for sleep problems does one bounded thing. It can show whether the thyroid is running too fast or too slow, and whether your iron stores are empty. Both are treatable, and both can run quietly for months before they are noticed.

It cannot show whether you stop breathing at night, whether stress is keeping you awake, or whether your sleep has drifted through habits built up over a long time. A test does not make a diagnosis on its own either. It produces values that have to be read together with how you feel.

A normal result is also an answer. It means the measurable explanations are settled and the question moves on to the things investigated another way. For some people that is a relief. For others it is the starting point for a conversation at a primary care centre about breathing, stress or habits.

This article is general health information, not medical advice and not an assessment of your values. If you have symptoms or concerns, contact your healthcare provider.