Waking up in the middle of the night is not a fault in itself. You sleep in cycles of roughly 90 minutes, and between two cycles you surface briefly. For most people that lasts seconds.
The trouble starts when you cannot get back to sleep afterwards.
What strikes me about the Dutch search results: mattress shops sit at the top, alongside a page claiming that waking at 3am says something about your liver. That claim comes from the traditional Chinese organ clock. Sleep research has never found anything of the sort.
There are causes you can actually check. Alcohol, night-time urination, restless legs, hot flushes, a busy head and snoring lead the list. For some of them your blood offers a starting point.
Why do you wake up at night?
Your sleep runs in cycles of about 90 minutes. At the end of each cycle you come close to wakefulness, and you surface for a moment. That happens four to six times a night. Usually you notice nothing. Only when something else joins in do you stay stuck in that waking phase.
That "something" is almost always identifiable. A full bladder, noise from outside, a warm bedroom, or a head that starts on tomorrow straight away.
Alcohol is the most underrated cause. A few glasses help you fall asleep faster, but in the second half of the night your sleep rebounds. You wake more often and your REM sleep shifts (PMID 23347102).
That rebound also shows up in people who otherwise sleep fine.
The Hersenstichting, the Dutch brain foundation, describes lying awake as a common complaint that often tracks with daytime tension. It matches what people report themselves: the body wakes up, and the head keeps it awake.
What research says does and does not help against lying awake sits in our piece on sleeping better.
Is it normal to wake up during the night?
Yes. Short interruptions belong to a normal night, and they increase with age. Over 50 you wake more often and for longer than you did at 25, without anything being wrong. The question that counts is not whether you wake, but how long you lie awake afterwards.
Sleep researchers often use a practical threshold. More than 30 minutes awake, more than three nights a week, for longer than three months. That pattern is called sleep maintenance insomnia.
Stay below it and you are usually dealing with one night that went differently than you hoped.
Persistently disturbed sleep tracks at group level with higher inflammatory values such as CRP and IL-6 (PMID 26140821). That is an association in large groups. It says nothing about your single bad night.
How much deep sleep you get and how that shifts over the years sits in the article on deep sleep.
What does it mean if you wake at 3am every night?
Usually nothing special about an organ. By 3am most of your deep sleep is behind you and your sleep turns lighter. Waking takes less of a nudge then than it does just after you drop off. The idea that this hour points to your liver comes from the traditional Chinese organ clock, not from sleep research.
I do understand why that explanation lands. It gives a sharp answer to a sharp question, and that feels better than "this is part of it".
Here is what does happen in those hours: your body temperature bottoms out, and your cortisol then climbs towards morning. If you wake around that point with a racing heart, tension is a more plausible lead than your liver.
The hour is also less fixed than it seems. You remember the night you looked at the clock and saw 3:12. The night you surfaced at 2:40 and sank straight back is gone from memory.
Turn your alarm clock around.
When does waking at night point to something physical?
When a physical sign comes with it that you also notice during the day. Snoring with gasping for air, legs that only settle once you move them, getting up to urinate several times, or waking soaked in sweat. Those are patterns to discuss with your GP, not to research for another evening.
Sleep apnoea is the most missed of them. An analysis in Lancet Respiratory Medicine estimated that roughly 425 million adults aged 30 to 69 worldwide have a moderate to severe form (PMID 31300334). Snoring, stalled breathing and dozing off during the day belong to that picture.
No blood value shows or rules out sleep apnoea. That needs a sleep study, and it runs through your GP.
Restless legs are the other blind spot. With restless legs syndrome you feel a strong urge to move your legs, mostly in the evening and at rest. Moving relieves it briefly, and then it wakes you again.
This is where iron comes in. A guideline from the American Academy of Sleep Medicine places iron status at the centre of restless legs management (PMID 39324694). Iron plays a part in dopamine handling in the brain, and with low stores the symptoms are often heavier.
Starting iron on your own is a poor idea while you do not know your values. Too much iron carries its own risks. What a ferritin value does and does not say sits in that article.
Frequent night-time urination is called nocturia. Evening fluids and caffeine play a part, and in men so does the prostate. Glucose and kidney function are among the things a doctor sometimes brings into it.
Thuisarts.nl, the patient information site Dutch GPs point to themselves, frames persistent sleep complaints as a reason to book a visit.
Which blood values are useful for sleep maintenance problems?
No blood value measures sleep. What blood can do is make visible a few physical contributors that keep the waking going: ferritin and transferrin saturation with restless legs, TSH with a thyroid running hot. Add FSH and oestradiol around menopause, and cortisol when you wake with a racing heart.
| Pattern you recognise | What often sits behind it | Blood value that can add insight |
|---|---|---|
| Waking with a racing heart and a busy head | Tension and a shifted cortisol rhythm can play a part | Morning cortisol, sometimes as a day curve |
| Getting up to urinate several times a night (nocturia) | Evening fluids and caffeine, in men also the prostate | Fasting glucose and HbA1c, creatinine and eGFR |
| Waking with hot flushes or drenched in sweat | Hormonal shifts around menopause, sometimes the thyroid | FSH and oestradiol, TSH |
| Restless legs that keep you awake | Restless legs syndrome, where iron status often plays a part | Ferritin and transferrin saturation |
| Snoring with gasping for air | Possibly sleep apnoea, which calls for a sleep study | No blood value: this belongs with your GP |
| Waking after an evening of alcohol | The rebound effect in the second half of the night | No test needed, the pattern speaks for itself |
The values in this table are not a diagnosis. They give your GP context for the pattern you describe, nothing more.
Picture two women of 44 who both wake around 3am and cannot keep their legs still. The first has a ferritin of 18 µg/L, the second 95 µg/L. Same complaint, different next step.
For the first, a low iron store is a plausible contributor. For the second that lead closes, and a doctor looks sooner at hormones or at breathing during the night.
Without that one number they both get the same advice: try going to bed earlier.
If the waking comes with sweating or hot flushes, night sweats goes deeper into that. If it comes with daytime tiredness, start at persistent fatigue.
To have a few of those values measured, you can do it directly with an iron studies panel or a cortisol test. Every result is reviewed by a BIG-registered doctor.
What to do first tomorrow morning
Start by writing things down instead of searching. For one week, note what time you woke, how long you lay awake, what you drank that evening and whether a physical sign came with it. That short list serves your GP better than a row of possible causes from a search engine.
Add three things. Whether your partner hears snoring or pauses in your breathing. Whether your legs feel restless in the evening. And how often you get up to urinate.
I would take that list to a GP once the pattern has run for three months or longer.
References
- Ebrahim IO, et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013. PMID 23347102.
- Benjafield AV, et al. Estimation of the global prevalence and burden of obstructive sleep apnoea: a literature-based analysis. Lancet Respir Med. 2019. PMID 31300334.
- American Academy of Sleep Medicine. Treatment of restless legs syndrome and periodic limb movement disorder: an American Academy of Sleep Medicine clinical practice guideline. J Clin Sleep Med. 2025. PMID 39324694.
- Irwin MR, Olmstead R, Carroll JE. Sleep disturbance, sleep duration, and inflammation: a systematic review and meta-analysis. Biol Psychiatry. 2016. PMID 26140821.
- Thuisarts.nl and the Hersenstichting. Public information on poor sleep and lying awake.
This article is informational and does not replace medical advice. Blood values are a snapshot and say nothing about a diagnosis on their own. Every result at Vitalcheck is reviewed by a BIG-registered doctor. If your symptoms persist or get worse, contact your GP.
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