Medically reviewed by Katelyn Hagerty, FNP
Written by Our Editorial Team
Last updated 8/24/2022
If you had to play a word association game with “erections” as your prompt, chances are good that you’d view descriptors like “long,” “strong” and “enjoyable” as positives -- things that you’d want to be associated with erections.
And that’s totally understandable. What’s not to love about erections? The longer your erection lasts and the stronger it is, the easier it is to have enjoyable sex with your partner.
But how long is too long? An erection is considered prolonged when it persists for four hours or longer, at which point it’s no longer caused by sexual or psychological stimulation, but is instead generally regarded as a medical emergency.
A prolonged erection is often referred to as “priapism.” This type of erection is often painful, and it requires prompt treatment to help you avoid experiencing permanent damage.
Below, we’ve gone into more detail about what priapism is, as well as the factors that can cause this condition to occur.
We’ve also discussed what you can do if you develop a prolonged erection, including when you should contact your healthcare provider or seek emergency medical treatment.
Priapism is a disorder in which the penis becomes erect for a long period of time, all without any obvious source of physical or mental sexual stimulation.
While there’s no exact amount of time an erection needs to last before it’s considered priapism, most experts agree that any penile erection that lasts for four hours or longer requires medical attention.
Priapism isn’t a common issue, but it’s an important phenomenon to be aware of, as prolonged erections can potentially lead to tissue damage and sexual performance issues such as erectile dysfunction (ED).
While priapism can occur in all age groups (including newborn children), it usually affects males between the ages of five to 10 and 20 to 50 years old.
There are three different types of priapism -- ischemic priapism (or low-flow priapism), recurrent ischemic priapism (stuttering priapism) and nonischemic priapism (often referred to as high-flow priapism). Each type of priapism causes distinct, unique symptoms.
Before we get into the specifics of each type of priapism, it’s important to briefly cover the basics of how erections work.
Erections start with mental or physical stimulation. When you feel sexually aroused, your central nervous system transmits messages to the tissue inside your penis, causing blood to flow to the corpora cavernosa -- two chambers of erectile tissue that give your penis its shape.
As blood flows into your corpora cavernosa, your penis becomes larger and firmer, allowing you to penetrate your partner. A membrane called the tunica albuginea wraps around the tissue and helps to keep blood inside your penis, allowing you to maintain your erection.
After you reach orgasm and ejaculate, this same process happens in reverse, with blood flowing out from your penis and your erection subsiding.
Priapism typically occurs when one or several issues interfere with outward blood flow from your penis, causing blood to flow unregulated or become trapped inside the erectile tissue.
Ischemic priapism, or low-flow priapism, occurs when there’s little or no blood flow in the tissue of your penis.
This type of priapism involves blood flowing into your penis normally when you become sexually aroused, but with little or no outward blood flow. Put simply, any blood that flows into your penis becomes trapped, causing the intracorporeal pressure (blood pressure in your penis) to rise.
As pressure builds inside your penis and your erection fails to properly subside, you may start to develop a rigid, prolonged erection and feel some degree of pain and discomfort.
This type of priapism is a medical emergency. If left untreated, the increasing pressure and lack of blood flow can lead to hypoxia (low oxygen levels), tissue ischemia (reduced nutrient supply) and acidosis (buildup of acid in the tissue of your penis).
Ischemic priapism is the most common form of priapism. Because of the potential damage it can cause to your penis, it’s important to seek medical attention as quickly as possible if you start to notice symptoms.
Recurrent ischemic priapism, or stuttering priapism, is a form of priapism that involves sustained and painful erections that resolve on their own.
This type of priapism often occurs at night and typically involves erections that become rigid for an extended period of time before eventually subsiding. Over time, these erections may begin to last for longer periods before naturally becoming flaccid.
Experts aren’t aware of precisely why this type of priapism develops, but evidence suggests that it may be associated with issues related to intracavernosal regulation caused by nitric oxide and phosphodiesterase type 5 (PDE5), an enzyme that controls penile blood flow.
There’s also some evidence that this type of priapism may be related to sickle cell disease and, in rare cases, cannabis use.
Stuttering priapism usually lasts for less than three hours. When this type of priapism happens on an ongoing basis, it can damage the penis and cause ED. As such, it’s important to talk to a healthcare provider if you often get prolonged, uncomfortable erections at night.
Nonischemic priapism, or high-flow priapism, occurs when there’s continuous blood flow to the erectile tissue, but the blood flow is unregulated and doesn’t become properly stored inside the penis.
This type of priapism can occur when a fistula, or abnormal connection, develops between the deep artery that supplies blood to your penis and the corpora cavernosa. This can occur after an injury that affects your penis and surrounding area.
Unlike ischemic priapism, nonischemic priapism typically doesn’t cause a significant amount of pain and usually isn’t a medical emergency.
The symptoms of priapism can vary in type and severity depending on the type of priapism you have. It’s important to pay close attention to your symptoms, as some forms of priapism require immediate medical attention.
If you have an ischemic priapism, you may develop the following symptoms:
Prolonged erections unrelated to sexual arousal. You may experience a prolonged erection that occurs without physical sexual contact or erotic imagery. An erection that lasts for more than four hours is generally considered priapism.
A firm, rigid penis with a soft glans. Priapism causes your penis to become firm, but the glans (tip of the penis) and corpus spongiosum (the area at the bottom of the penis) may remain soft.
This difference in firmness occurs because these areas of tissue have their own venous drainage system that’s separate from the main erectile tissue of the penis.
Pain that may worsen over time. Ischemic priapism is usually painful. Your penis may begin to hurt after it becomes erect, with pain worsening as the level of pressure in your erectile tissue increases.
Ischemic priapism is a serious medical emergency. If you notice any of the symptoms above, it’s important to seek medical care as soon as you can.
Nonischemic priapism causes slightly different symptoms than ischemic priapism. With this type of priapism, your penis may feel firm but not completely rigid. Nonischemic priapism is generally not painful, with minimal tenderness or discomfort.
It might not seem like it, but getting an erection is a surprisingly complex process that depends on the collaborative efforts of your muscular, nervous and circulatory systems.
Erections develop in response to sexual stimulation. This can be mental stimulation -- having a sexual thought or dream, for example -- or sensory stimulation, such as being touched by your partner in a sexual way.
As we mentioned above, this process stimulates blood flow to your penis, causing your penis to become firmer and larger as your blood vessels close up hold the inflow of blood in your erectile tissue.
Normally, blood flows out from your penis after you reach orgasm and ejaculate, or when you’re no longer sexually stimulated.
In the event that this normal flow of blood is disrupted, your erection can persist for a prolonged period, resulting in priapism.
A variety of issues can potentially affect blood flow and cause priapism, including disorders that affect your blood, medications, injuries to your penis and lifestyle factors.
Hematological disorders such as sickle cell disease and leukemia are common potential causes of priapism. Sickle cell anemia is an especially common cause of prolonged erections, with data suggesting that at least 42 percent of adult men with the condition will experience priapism.
Priapism can occur in men with sickle cell disease due to sickled red blood cells, which can stop blood flow out from the penis. Leukemia can also affect outward blood flow and stop blood from properly leaving the penile tissue.
Other blood disorders, such as thalassemia, can also affect blood flow from the penis and cause priapism.
Certain medications can increase your risk of developing priapism, including certain medications for treating erectile dysfunction.
More specifically, PDE5 inhibitors such as sildenafil (the active ingredient in Viagra®) and other medications for erectile dysfunction are associated with increased blood flow to the penis and a higher incidence rate of priapism.
Based on media coverage, it’s easy to get the impression that prolonged, painful erections are a common side effect of ED medication.
This isn’t accurate. Although medications like Viagra can cause side effects, priapism is a highly uncommon issue. In fact, it only affects a fraction of a percentage of men who use ED medication.
Experts estimate that in total, only about 0.73 cases of priapism occur per 100,000 men every year.
To put these numbers in perspective, an estimated 30 million men in the United States have ED, with millions of men using medications such as Viagra, Cialis and their generic equivalents on a frequent basis.
Other medications that can cause priapism include antidepressants, antipsychotics, medications for hypertension and/or heart disease, as well as injectable medications that are used directly to increase blood flow to the penis.
It’s important to inform your healthcare provider if you experience prolonged or painful erections after starting treatment with a new medication.
Injuries to your penis can affect the blood vessels that control blood flow into and out from your penis, potentially causing priapism.
Injuries to your penis and surrounding area can develop from accidents, sporting injuries or as complications from surgery to the bladder or prostate. Injuries that damage your penis typically cause non-ischemic priapism.
Some illicit drugs, including cocaine, are associated with an increased risk of priapism or other sexual function issues. Alcohol is also a known contributing factor in many cases of ischemic priapism.
In addition to blood disorders, medications and penile trauma, priapism may also be caused by metabolic disorders like gout, diabetes and renal failure.
Other issues that can cause priapism include neurogenic disorders such as spinal cord injuries, as well as cancers that affect the penis (referred to as malignant priapism).
While ischemic and nonischemic priapism are both characterized by prolonged erections, they have distinct causes and treatments.
This makes accurately diagnosing the type of priapism you have particularly important, as the most effective treatment for one form of priapism may not be suitable for the other.
If you have a prolonged or painful erection, it’s important to seek medical attention as soon as you can.
Your healthcare provider will likely ask you questions about your symptoms, including any pain you feel. You may also be asked about your medical history, whether you have previously hurt your penis, if you’ve used any alcohol or drugs recently and other questions.
Your healthcare provider may perform a physical examination. During this physical exam exam, your penis may be inspected for signs of trauma, cancers or other medical conditions that could cause painful and/or extended erections.
In some cases, your healthcare provider may be able to determine the correct type of priapism simply by asking questions and inspecting your penis.
Your healthcare provider may also use certain tests to determine the type of priapism you have and the potential cause of your issues. These may include:
Diagnostic ultrasound. This test involves scanning your penis using sound waves to create an image of your penis’s internal structure. Ultrasound imaging can help to find fistulas and other injuries that may cause priapism.
Blood gas testing. Testing for intracorporeal blood gasses (gasses in the tissue of your penis) can help to identify ischemic priapism and provide information about any damage to your penis.
Blood gas measurement is an invasive procedure that requires the insertion of a small needle into the tissue of your penis.
Blood testing. Your healthcare provider may also request other tests, such as a blood test. Comprehensive blood work can often identify problems that contribute to priapism, such as signs of sickle cell disease or leukemia.
Doppler ultrasound. This type of test uses high-frequency sound to measure the level of blood flow in the blood vessels of your penis. It may reveal narrowed blood vessels, a blockage, abnormal blood flow or an aneurysm (bulge in a blood vessel).
Penile blood gas analysis. This test involves taking a sample of blood from your penis using a small needle. The staff at the hospital will analyze the blood and check the level of carbon dioxide and oxygen gas, which can signal an ischemic priapism.
Magnetic resonance imaging (MRI). This type of test may help to detect blood clotting or tumors. Magnetic resonance angiography (MRA), another type of test, may be used to evaluate blood vessels inside your penis.
Blood test. You may be asked to provide a blood sample. This assists in detecting and diagnosing conditions that may cause ischemic priapism, such as sickle cell disease or certain forms of cancer.
Toxicology test. You may be asked to provide a blood or urine sample for a toxicology test. This test helps to detect drugs, medications or other substances that may cause priapism.
Your healthcare provider may also request a urine sample if drugs -- particularly a recreational drug -- are the potential cause of priapism.
It’s normal to occasionally to get random erections without sexual stimulation. For example, you might have an erotic thought that causes you to feel sexually stimulated, even if you aren’t with your partner or in the mood for sex.
Sometimes, you may notice that it takes longer than usual -- often a few minutes or more -- for these erections to go away.
While the occasional long-lasting erection usually isn’t a serious problem, it’s important to seek immediate medical help if you have a painful erection, or an erection that lasts longer than four hours.
If you think you may have ischemic priapism, you should call 911 or go to your nearest hospital emergency room as soon as you can.
To understand the urgency of treating ischemic priapism, here’s what can happen to your penis when an erection lasts longer than four hours.
First, the blood trapped inside the shaft of your penis can become deprived of oxygen, which in turn damages the penile tissue. Over time, this can prevent the tissue from functioning correctly and cause you to develop permanent erectile dysfunction.
Studies have found that ischemic priapism that lasts for longer than 24 hours has a 90 percent chance of causing erectile dysfunction. Put simply, if you don’t seek treatment for priapism as soon as you can, your odds of getting an erection in the future aren’t particularly good.
Healthcare professionals employ several methods of treatment for priapism, usually from least invasive to most invasive, depending on what works and what doesn’t.
These include using oral medications such as pseudoephedrine, penile injection and aspiration, intracavernosal drug therapy and, when other methods of treatment fail, surgical procedures to drain blood from the penis and reduce the risk of permanent injury.
Research has found that penile injection and aspiration, which involves injecting medication into the penis and manually removing blood using a small needle, works more than 80 percent of the time for men with ischemic priapism.
When it comes to recurrent or “stuttering” priapism, treatment usually involves the long-term use of medication to prevent painful or prolonged erections from returning.
When priapism is caused by sickle cell disease, treatment may involve hydration, alkalinization, oxygenation, and pain control of the penis, in addition to conventional treatments for priapism.
Nonischemic priapism is often treated using ice packs and careful monitoring. It’s rare for this type of priapism to require embolization or surgery, although these procedures may be used for cases that don’t improve over time or cause significant discomfort.
It’s normal -- and, in several ways, a sign of good health -- to get random erections. It’s also a good thing to be able to maintain your erections for a long time, especially when you’re having sex.
However, erections that feel uncomfortable, cause you noticeable pain or last for several hours at a time definitely aren’t normal.
If you have a painful or unusual persistent erection, it’s important to seek medical help as soon as you can. If you have ischemic priapism, your healthcare provider may perform a procedure, give you medication or take other steps to drain your penis of blood and prevent injury.
You can get help by calling 911 or driving to your nearest hospital. Since ischemic priapism is a serious medical emergency, it’s important to act as quickly as possible if you develop any of the symptoms above.
Interested in learning more about erectile health? We offer a range of medications for ED online, including evidence-based options such as sildenafil (the active ingredient in Viagra) and tadalafil (the active ingredient in Cialis®).
You can also learn more about improving your sexual function naturally in our complete guide to healthy habits for better sexual performance.