What morning wood says about your health

Men are supposed to wake up with an erection every morning. Seriously, if you're in "good health," your body is hard-wired for "morning wood." If you don't regularly wake up with that familiar morning erection, it could indicate that your testosterone levels, blood flow, or something more serious is off. 

Erectile dysfunction

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Nocturnal erections (erections that happen while you’re sleeping) are part of having a penis—and they start young. Healthcare providers have noted erections in fetuses during ultrasounds, and even young boys experience erections throughout childhood, long before the onset of puberty. 

In fact, nocturnal erections—also known as "sleep-related erections" (SREs) or "nocturnal penile tumescence" (NPT)—and morning erections are so ordinary that their presence (or absence) can be an essential indicator of a man's overall health.

Healthy men typically experience morning wood throughout their lives. If you aren’t getting normal morning erections, talk to your healthcare provider, as this could be a sign of a more serious problem. 

While there's no shortage of evidence for the existence of morning and nocturnal erections, nobody knows the exact reasons for morning erections. Here's what we do know about erections and sleep. 

Men typically have five nocturnal erections during an eight-hour sleep cycle, with each erection lasting about 25 minutes. That's about one erection every 90 minutes. It didn't take long for researchers to note that this pattern was strikingly similar to another 90-minute cycle that occurs during sleep—REM (rapid eye movement) phase sleep (Youn, 2017). 

Erections and REM sleep 

Researchers have known about the relationship between REM sleep, or the dreaming phase of sleep, and nocturnal erections for years, fueling several decades of speculation about what really happens during REM sleep to cause erections. Essentially, men slip into REM sleep about an hour and a half after dozing off. Each episode of REM sleep corresponds with an erection lasting 20 to 25 minutes (Youn, 2017).

Despite this relationship between REM sleep and erections, scientists still don't know why morning wood happens—but they have some ideas.

Theories behind nocturnal erections

Nocturnal erections may be caused by norepinephrine production slowing down during REM sleep (Becchetti, 2016). Norepinephrine is the chemical primarily responsible for keeping the penis relaxed (Panchatsharam, 2021). In other words, the part of the brain that maintains norepinephrine levels gets turned down during REM sleep. This lets the testosterone-related excitatory mechanisms take over, leading to an erection.

Another theory is that you get morning wood because your body produces more nitric oxide during REM sleep. Nitric oxide is responsible for making the blood vessels of the penis relax, allowing all the extra blood needed to cause an erection to enter the penis (Brown, 2012). 

The bottom line is that no one really knows what role REM sleep plays in nocturnal penile tumescence. Why do men get nighttime erections (many times) a night? Are morning wood and REM sleep linked, or is it just an interesting coincidence? There are a lot of theories.

So many things have to go right for you to achieve a strong erection.

You have to release hormones on-demand and dilate arteries to carry blood to the penis. Your nervous system has to transmit signals perfectly, and your mind has to be in harmony with your body. There's a lot that can go wrong. If you're having difficulty getting erections, it could be due to several serious health risks. 

The blood vessels of the penis are also small compared to other areas of the body. That means other underlying conditions can show up first as erectile dysfunction (ED). ED could indicate high cholesterol levels, stress, type 2 diabetes (or prediabetes), hypertension (high blood pressure), depression, sleep disorders, heart disease, hormone issues, side effects of medication, consequences of lifestyle choices, emotional issues, or more (Sooriyamoorthy, 2021). 

Erectile dysfunction isn't just a problem for older men. An increasing number of young men are diagnosed with ED every year. Studies estimate that as much as 30% of young men (under 40 years old) experience erectile dysfunction (Nguyen, 2017). 

ED may be due to multiple issues like stress or decreased sex drive, combined with medical issues like high blood pressure, diabetes, heart disease, among others. 

The good news? There is help available if you experience ED. Learn more about treatments here. 

Pay attention to your morning wood. The loss of that familiar morning erection could be more than just a problem with sexual health—it may be the first sign of a significant medical problem (Capogrosso, 2017). If you aren't getting morning wood, see your healthcare provider.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Current version

August 11, 2021

Written by

Health Guide Team

Fact checked by

Chimene Richa, MD

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About the medical reviewer

Chimene Richa, MD

Dr. Richa is a board-certified Ophthalmologist and medical writer for Ro.