Why Am I Not Getting Enough Deep Sleep?

Key takeaways:

• Deep sleep is the most physically restorative stage of sleep. It's when your body repairs tissue, supports immune function, and clears waste from the brain.

• Stress, alcohol, caffeine, irregular schedules, and sleep disorders like obstructive sleep apnea are common causes of low deep sleep.

• Lifestyle changes can help. But if your deep sleep stays low despite good habits, a sleep study may be needed to find out what's going on.

You're spending 7 or 8 hours in bed, but you still wake up feeling like you didn't sleep at all. Your sleep tracker might be showing 30 or 40 minutes of deep sleep. Or maybe you just feel it — the fatigue, the brain fog, the sense that sleep isn't doing its job.

Deep sleep is the stage your body relies on for physical recovery. When you're not getting enough, the effects show up during the day. Understanding what disrupts deep sleep — and what you can do about it — is the first step toward feeling rested again.

What is deep sleep?

Sleep happens in cycles, each lasting about 90 to 120 minutes. Within each cycle, your brain moves through four stages:

• Stage 1 (N1): Light sleep. You're drifting off and can be easily woken.

• Stage 2 (N2): Your heart rate slows and body temperature drops. This makes up the largest share of your total sleep.

• Stage 3 (N3): Deep sleep, also called slow-wave sleep. Brain activity shifts to slow delta waves. Heart rate, breathing, and muscle activity all reach their lowest levels.

• REM sleep: Brain activity increases to near-waking levels. This is when most vivid dreaming occurs.

Deep sleep is concentrated in the first half of the night. As the night goes on, each cycle contains less deep sleep and more REM sleep. This is why disruptions early in the night — like falling asleep late or waking up shortly after — tend to affect deep sleep more than other stages.

What does deep sleep do?

Deep sleep supports several biological processes that are less active during lighter sleep stages:

• Tissue repair and growth: The pituitary gland releases growth hormone during deep sleep, which stimulates tissue repair, muscle recovery, and cell regeneration.

• Immune function: The body produces cytokines — proteins involved in fighting infection and inflammation — primarily during this stage.

• Memory consolidation: The brain transfers information from short-term to long-term storage during slow-wave sleep. This is especially important for declarative memory (facts and events).

• Brain waste clearance: The glymphatic system, the brain's waste-removal network, becomes significantly more active during deep sleep. It clears metabolic byproducts, including beta-amyloid proteins associated with Alzheimer's disease.

When deep sleep is consistently insufficient, these processes don't fully complete. That can show up as persistent fatigue, difficulty concentrating, slow recovery from exercise, and getting sick more frequently.

Also Read: Why Sleep is Important for Your Health

How much deep sleep do you need?

Most adults spend about 10% to 25% of their total sleep time in deep sleep. For someone sleeping 7 to 8 hours, that works out to roughly 45 to 110 minutes per night.

Several factors affect how much deep sleep you get:

• Age: Deep sleep declines naturally with age. Young adults may spend 20% to 25% of their sleep in deep stages. By age 60, that number may drop to 5% to 10%.

• Physical activity: People who are more physically active tend to spend more time in deep sleep.

• Individual variation: Some people naturally get more or less deep sleep, even with similar habits.

What about sleep trackers? Consumer devices like Oura, Apple Watch, and Fitbit estimate sleep stages using movement and heart rate data. They're useful for identifying trends, but they're not as accurate as a polysomnography (sleep study). Most trackers can distinguish sleep from wakefulness reasonably well, but they're less reliable when it comes to separating deep sleep from other stages.

If your tracker consistently shows low deep sleep and you're experiencing daytime symptoms, it's worth paying attention, but don't treat the numbers as exact.

What causes low deep sleep?

Many things can reduce the amount of time you spend in deep sleep. Some are habits. Others are medical conditions that may need treatment.

Stress and high cortisol

Cortisol, the body's primary stress hormone, normally peaks in the morning and falls to its lowest levels at night. Chronic stress disrupts this pattern, keeping cortisol elevated into the evening. That keeps the nervous system in a sympathetic (fight-or-flight) state, which makes it harder for the body to transition into deep sleep.

People under chronic stress often report sleeping "enough" hours but still feeling exhausted. This is a common reason the total sleep time is adequate, but the sleep architecture is skewed toward lighter stages.

Alcohol

Alcohol is sedating, which is why it can help you fall asleep faster, but it disrupts normal sleep stages. In the first half of the night, alcohol tends to increase deep sleep. As the body metabolizes it, the second half of the night becomes lighter and more fragmented, with more awakenings and less REM sleep.

This effect is dose-dependent. Even one to two drinks can measurably reduce sleep quality.

Caffeine

Caffeine has a half-life of about 5 to 6 hours. It works by blocking adenosine, a neurotransmitter that builds homeostatic sleep pressure throughout the day. That pressure is one of the main drivers of deep sleep.

Caffeine consumed in the mid-afternoon can still be active at bedtime. You may fall asleep without difficulty but spend less time in slow-wave sleep.

Inconsistent sleep schedule

Your circadian rhythm — the internal clock that regulates sleep-wake cycles — depends on consistency. 

Deep sleep is most abundant in the first few hours after sleep onset, and your body expects those hours to occur at a predictable time.

Shifting your bedtime by an hour or more between weekdays and weekends creates what sleep experts call "social jet lag." It disrupts sleep stages in a way that's similar to crossing time zones.

Blue light and screen use

Light-sensitive cells in the eyes respond to short-wavelength (blue) light from screens. This suppresses melatonin production and can delay sleep onset. Because deep sleep is concentrated early in the night, even a modest delay in falling asleep can cut into slow-wave sleep time.

Stimulating content — news, social media, work email — also keeps the brain in an active state when it should be winding down.

Sleep environment

Deep sleep is easily disrupted by environmental factors:

• Temperature: The body needs to cool slightly to initiate and maintain deep sleep. A warm bedroom works against this process. Most guidelines recommend around 65°F (18°C).

• Noise: Even sounds that don't fully wake you can trigger micro-arousals that shift you into lighter sleep.

• Light: Any ambient light — including standby LEDs from electronics — can interfere with melatonin production and sleep quality.

Late meals and napping

Large meals close to bedtime keep the digestive system active and can cause acid reflux, which fragments sleep. Long or late-afternoon naps reduce homeostatic sleep pressure — the accumulated need for sleep that helps drive you into deep stages at night.

Medications

Some medications affect sleep as a side effect:

• Beta-blockers can suppress melatonin production.

• Certain antidepressants (particularly SSRIs) may fragment sleep continuity.

• Corticosteroids can increase alertness and reduce deep sleep.

If your sleep quality changed around the time you started a new medication, mention it to your prescriber. Adjusting the dose or timing may help.

Sleep disorders & other conditions

Several conditions directly reduce deep sleep, and many go undiagnosed:

• Obstructive sleep apnea (OSA): Repeated airway collapses cause brief arousals that pull you out of deeper stages. Classic signs include loud snoring, gasping during sleep, and excessive daytime sleepiness. Recent estimates suggest tens of millions of U.S. adults have undiagnosed OSA.

• Upper airway resistance syndrome (UARS): A milder form of sleep-disordered breathing that causes frequent micro-arousals without full apneas. It's more common in younger, thinner individuals and women, and it's often missed on standard sleep studies.

• Restless legs syndrome (RLS): An uncomfortable urge to move the legs, especially in the evening, that delays sleep onset and causes awakenings.

• Periodic limb movement disorder: Involuntary leg movements during sleep that trigger brief arousals. Many people don't know they have it until a sleep study detects it.

• Bruxism: Teeth grinding causes micro-arousals throughout the night. It's often discovered when a dentist notices tooth wear or a partner hears grinding.

• Chronic pain: Conditions like fibromyalgia and arthritis keep the body in a semi-alert state, reducing time in slow-wave sleep.

• PTSD and anxiety disorders: These conditions can cause hypervigilance that persists into sleep, preventing your body from winding down as needed for deep sleep. Nightmares, frequent awakenings, and fragmented sleep are common, particularly in PTSD.

If lifestyle changes aren't improving your deep sleep, an undiagnosed sleep disorder may be the reason.

Aging

Deep sleep naturally declines with age. This is normal and expected. But it also means that other factors — stress, alcohol, medications, inconsistent schedules — have a greater impact than they might have had in your 20s or 30s. There's less of a buffer.

Also Read: 7 Sleep Myths That Are Keeping You Awake (And What Actually Works)

How can you improve deep sleep?

The strategies below target the most common causes of low deep sleep. Some may help quickly. Others take consistency before you see results.

Manage stress before bed

A regular wind-down routine helps your body shift from active mode to rest. Approaches that have evidence behind them include:

• Deep breathing exercises (such as the 4-7-8 technique)

• Progressive muscle relaxation

• Gentle stretching or restorative yoga

• Journaling

• A warm bath or shower, the post-bath temperature drop mimics the body's natural cooling before sleep

Consistency matters more than which technique you choose. A routine that signals "it's time to sleep" helps the body prepare.

Adjust caffeine and alcohol intake

Move your caffeine cutoff to early afternoon or noon if you're particularly sensitive. For alcohol, stop at least 3 to 4 hours before bed. If you suspect alcohol is affecting your sleep, try eliminating it for 2 to 3 weeks and see if your symptoms improve.

Keep a consistent sleep schedule

Go to bed and wake up at the same time every day, including weekends. If your schedule varies by more than about an hour, your circadian rhythm may not be optimally aligned with your sleep window.

Optimize your sleep environment

• Keep the bedroom cool — around 65°F (18°C).

• Use blackout curtains or a sleep mask.

• Reduce noise with earplugs or a white noise machine.

• Cover or remove standby LED lights.

• Make sure your mattress and pillow provide adequate support.

Limit screen time before bed

Put screens away at least 1 hour before bed. Night mode reduces blue light but doesn't eliminate the stimulating effect of the content. Reading, stretching, or listening to calm music are better alternatives.

Exercise regularly

Regular physical activity — both aerobic exercise and resistance training — is one of the most evidence-supported ways to increase deep sleep. Aim for at least 150 minutes of moderate exercise per week. Finish intense workouts at least 4 hours before bedtime.

Consider a natural sleep aid

If stress and anxiety are keeping you from winding down at night and you've already addressed the basics, a targeted supplement may help.

Sip2Sleep® contains Venetron®, a plant-based ingredient derived from rafuma leaf that has been studied for its calming effects on the body. Helping reduce stress and anxiety before bed, it supports the body's ability to transition into deeper, more restorative sleep. It also includes Montmorency tart cherry extract, which provides anti-inflammatory anthocyanins and supports natural melatonin production.

Unlike standalone melatonin supplements, which primarily affect sleep timing and onset, this combination addresses the stress response that often prevents deep sleep in the first place.

Frequently asked questions

How do I know if I'm getting enough deep sleep?

The most reliable indicator is how you feel during the day. If you consistently wake up tired, have difficulty concentrating, recover slowly from physical activity, or get sick more often — despite adequate total sleep time — low deep sleep may be a factor. Sleep trackers can show trends, but only a clinical sleep study can accurately measure sleep stages.

Does melatonin increase deep sleep?

Melatonin primarily helps with sleep timing and onset. It signals the brain that it's time to sleep and may help you fall asleep faster, but it does not reliably increase time spent in slow-wave sleep. If your deep sleep is low because of stress, caffeine, alcohol, or a sleep disorder, melatonin is unlikely to address the underlying cause.

Does exercise help with deep sleep?

Yes. Regular physical activity — particularly aerobic exercise and resistance training — has been shown to increase slow-wave sleep. Timing matters: intense exercise close to bedtime can raise cortisol and core body temperature, which may delay sleep onset.

Can you get too much deep sleep?

This is uncommon. The body naturally regulates how much time it spends in each sleep stage. If your tracker shows unusually high deep sleep, it may reflect a measurement limitation rather than an actual problem. However, if you're sleeping excessively and still feel fatigued, it's worth discussing with your doctor.

The bottom line

Deep sleep is essential for physical recovery, immune function, memory, and brain health. Many people don't get enough of it, and the causes are often things like stress, alcohol, caffeine, irregular schedules, or undiagnosed sleep disorders. The good news is that most of these are addressable. Start with the lifestyle factors you can control, and see a healthcare professional if things don't improve.

References

1. Patel AK, Reddy V, Shumway KR, et al. Physiology, Sleep Stages. [Updated 2024 Jan 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK526132/

2. National Heart, Lung, and Blood Institute. Sleep Phases and Stages. How Sleep Works. National Institutes of Health; 2022 Mar 24. https://www.nhlbi.nih.gov/health/sleep/stages-of-sleep

3. National Institute of Neurological Disorders and Stroke. (2025, February 25). Brain basics: Understanding sleep. National Institutes of Health. https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep

4. Pietilä J, Helander E, Korhonen I, Myllymäki T, Kujala UM, Lindholm H. Acute Effect of Alcohol Intake on Cardiovascular Autonomic Regulation During the First Hours of Sleep in a Large Real-World Sample of Finnish Employees: Observational Study. JMIR Ment Health. 2018 Mar 16;5(1):e23. doi: 10.2196/mental.9519. PMID: 29549064; PMCID: PMC5878366.

5. Nathaniel Watson, Kristina Yu, David Campbell, Lisa Bloudek, John Yee, John Cronin, Ana Sanchez Azofra, Nikolina Boskovic, 0637 Prevalence and Unmet Need of Obstructive Sleep Apnea in the United States, Sleep, Volume 48, Issue Supplement_1, May 2025, Page A278, https://doi.org/10.1093/sleep/zsaf090.0637

6. Sankari A, Maggard MD, Cascella M. Upper Airway Resistance Syndrome. [Updated 2025 Aug 2]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK564402/