Waking up at 3am every night: what cortisol, alcohol and blood sugar have to do with it

You fall asleep easily. But then you are suddenly wide awake, you glance at the clock: 3:12am. Again. Your thoughts start to race, your heart beats a little faster, and sleep is out of the question for now. In the morning the alarm goes off, and you feel completely wiped out.

Many people know this: waking up at the same time every night, usually between 3 and 4am. This article explains what happens in your body at this time, what role cortisol, alcohol and blood sugar can play and what can help you get to the bottom of the cause.

What happens in your body between 3 and 4am

The body follows an internal clock. In the evening, the sleep hormone melatonin rises, and the stress hormone cortisol is at its lowest. In the second half of the night, this relationship slowly reverses: cortisol starts to rise in the early hours of the morning and reaches its peak shortly after waking up (PubMed 23148157). This is how the body prepares to be awake and alert.

At the same time, sleep becomes lighter in the second half of the night. Short waking phases are completely normal then – most people simply do not notice them. It becomes a problem when you wake up fully and cannot get back to sleep.

Waking up at night and cortisol: what stress has to do with it

With ongoing stress, the body’s stress system is often already active when it should actually be at rest. In a sleep lab study, people with chronic insomnia had more cortisol and ACTH in their blood over 24 hours than good sleepers in the comparison group – the biggest differences were in the evening and in the first half of the night (PubMed 11502812). The worse they slept, the more cortisol they released.

This means: if you are stressed, it is harder to drift off again after a natural short waking phase. If thoughts about the next day then come in, you become more awake – and frustration about being awake makes it even worse.

Waking up at night after drinking alcohol

A glass of wine in the evening helps many people fall asleep. But a review of all studies on alcohol and sleep shows a clear pattern: alcohol shortens the time it takes to fall asleep and makes the first half of the night deeper, but disrupts sleep in the second half of the night (PubMed 23347102). Precisely when the alcohol has been broken down, you wake up more often. This applies even to smaller amounts.

Other reasons for waking up at night

• Pauses in breathing (sleep apnoea): Loud snoring with pauses in breathing, morning headaches and severe daytime tiredness can be signs. Sleep apnoea is very common worldwide and often goes unrecognised for a long time (PubMed 31300334). It should be checked by a doctor.
• Blood sugar: A late, very sugary meal or, in people with diabetes, low blood sugar at night can disturb sleep. If you take insulin or blood-sugar-lowering tablets and wake up at night sweating, shaking or with palpitations, you should discuss this with your doctor.
• Menopause: Hot flushes and night sweats wake many women during this phase of life.
• Needing to urinate, pain, heartburn: Physical reasons also interrupt sleep.
• Light, noise, warmth: A bedroom that is too warm or too bright makes the light sleep of the second half of the night more easily disturbed.

If you take medication that may affect your sleep, mention this to your doctor. Do not stop a prescribed medication without talking to your doctor first.

What you can do yourself

• Do not look at the clock. Knowing the time puts many people under pressure.
• If you lie awake for a long time, get up and do something calm in dim light until you feel tired again.
• Cut down on alcohol in the evening and see whether the second half of the night changes.
• Fixed wake-up times, even at the weekend.
• Write down your thoughts before going to sleep, so that they do not pop up at 3am.

For longer-lasting sleep problems, the European guideline recommends cognitive behavioural therapy for insomnia as the first choice, which is also available as a digital application (PubMed 28875581). Ask your doctor about it.

Measuring cortisol and melatonin

If you would like to know what your own daily rhythm looks like, you can have cortisol and melatonin measured in your saliva:

• The Cortisol daily profile measures cortisol in the morning, at midday and in the evening, as well as DHEA. It shows the course over the day, not a night-time value.
• The Melatonin test measures the sleep hormone in a saliva sample that you take at 2am in the dark.
• The Stress & sleep lab package combines both with further analyses of the stress axis.

The values are building blocks for a conversation, not a diagnosis. The ORY expert team or your doctor can support you in interpreting them.

In brief

• In the second half of the night, sleep becomes lighter and cortisol starts to rise.
• With chronic stress and insomnia, the stress system is often more active at night too.
• Alcohol makes it easier to fall asleep but disrupts the second half of the night.
• Pauses in breathing, blood sugar, menopause and physical reasons are also possible causes.
• A cortisol daily profile and a melatonin test show your own rhythm.

Frequently asked questions

Why do I wake up at 3am every night?

In the second half of the night, sleep is lighter and cortisol starts to rise (PubMed 23148157). Stress, alcohol in the evening, pauses in breathing, hot flushes or a restless sleep environment then make it more likely that you wake up fully.

Is waking up at night linked to cortisol?

It can be. In one study, people with chronic insomnia had more cortisol, especially in the evening and in the first half of the night (PubMed 11502812). However, a single value does not explain waking up at night on its own.

Why do I wake up in the night after drinking alcohol?

Alcohol deepens sleep in the first half of the night, but disrupts it in the second half, when it is broken down (PubMed 23347102).

What helps if I wake up at night and can’t get back to sleep?

Do not look at the clock, get up briefly and do something calm if you lie awake for longer, and keep fixed wake-up times. For persistent sleep problems, cognitive behavioural therapy for insomnia is the first choice (PubMed 28875581).

When should I see a doctor about waking up at night?

If the sleep problem lasts for weeks, severely affects you during the day, you snore loudly with pauses in breathing, you wake up at night with a racing heart, shortness of breath or heavy sweating, or you take medication that could affect your sleep.

Can measuring cortisol help explain waking up at night?

A cortisol daily profile in saliva shows the course over the day, and a melatonin test shows the value at night. Both can help you better understand your own rhythm – together with a conversation about sleep habits and stresses.

Sources

1. Chan S, Debono M. Replication of cortisol circadian rhythm. Ther Adv Endocrinol Metab. 2010. PubMed 23148157
2. Vgontzas AN et al. Chronic insomnia is associated with nyctohemeral activation of the hypothalamic-pituitary-adrenal axis. J Clin Endocrinol Metab. 2001. PubMed 11502812
3. Ebrahim IO et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013. PubMed 23347102
4. Benjafield AV et al. Estimation of the global prevalence and burden of obstructive sleep apnoea. Lancet Respir Med. 2019. PubMed 31300334
5. Riemann D et al. European guideline for the diagnosis and treatment of insomnia. J Sleep Res. 2017. PubMed 28875581