Internal bleeding doesn’t always announce itself with dramatic symptoms. In many cases, the signs are subtle at first: unexplained dizziness, growing fatigue, or a heart rate that climbs for no obvious reason. Because the blood stays inside your body, you can’t see it the way you would with an external wound, which makes knowing what to look for especially important.
Early Warning Signs Most People Miss
The earliest symptoms of internal bleeding often mimic things you might brush off as dehydration or exhaustion. When you’ve lost between 15% and 30% of your blood volume, you may notice dizziness or lightheadedness, fatigue and weakness, nausea, shortness of breath, and a heart rate that feels faster than usual. These symptoms show up because your body is working harder to circulate a shrinking blood supply.
At this stage, your blood pressure may still look relatively normal on a monitor, which is part of what makes internal bleeding tricky. Your body compensates by squeezing blood vessels tighter and pumping faster. The bottom number on a blood pressure reading actually rises at first before the top number eventually drops. So “normal” vitals don’t rule out bleeding, especially if you feel off after an injury or have risk factors.
Once blood loss crosses 30% of your total volume, the body can no longer compensate. Confusion, seizures, and loss of consciousness can follow. At this point, the situation is a medical emergency called hypovolemic shock, where organs start shutting down from lack of blood flow.
Signs That Depend on Where the Bleeding Is
Internal bleeding produces different clues depending on which part of the body is affected. Knowing the location-specific signs can help you recognize what’s happening before the situation becomes critical.
Abdomen and Torso
Bleeding inside the abdomen often causes pain, swelling, or a feeling of tightness. Two visible skin changes are particularly telling. Bruising and swelling around the belly button (called Cullen sign) suggests bleeding inside the abdominal cavity. Bruising along the side of your body between the ribs and hip points to bleeding behind the abdominal organs. Both of these skin changes can take up to 48 hours to appear, so they won’t help you catch bleeding right away, but they’re a strong signal that something serious has been happening internally. Mild bleeding produces yellowish bruising, while more severe bleeding turns the skin dark blue, purple, or black.
Digestive Tract
Bleeding in the stomach or upper intestines often shows up as black, tarry stool. The dark color comes from blood being partially digested as it moves through your system. Bleeding lower in the digestive tract, such as in the colon, tends to produce bright red blood mixed with or on top of stool. Some people with chronic, slow gastrointestinal bleeding notice their stool alternating between black and bloody over weeks, sometimes with no pain at all. Vomiting material that looks like dark coffee grounds is another sign of bleeding in the stomach or esophagus.
Inside the Skull
Bleeding inside or around the brain can develop hours or even days after a head injury. The hallmark symptom is a headache that keeps getting worse instead of fading. As pressure builds, other neurological symptoms follow: drowsiness that deepens over time, confusion, vomiting, slurred speech, dizziness, and blurred vision. One particularly telling sign is pupils that become different sizes. You may also lose movement or strength on one side of the body, opposite to the side of the injury. Seizures and loss of consciousness indicate the bleeding has reached a dangerous level.
Who Is at Higher Risk
Certain medications significantly raise your chances of internal bleeding, and they can also make bleeding harder to stop once it starts. Blood thinners fall into two main categories: those that slow clotting and those that prevent blood cells from sticking together. Taking one type carries a roughly 4% annual risk of gastrointestinal bleeding. Taking both types together nearly doubles that risk to about 7.4%. People 75 and older face twice the bleeding risk of younger patients when on combination blood thinners.
Beyond medications, conditions like liver disease, hemophilia, and other clotting disorders make internal bleeding more likely and more dangerous. Recent surgery, major trauma, and heavy alcohol use are also risk factors. If you take blood thinners and notice any of the symptoms described above, especially black stool, unusual bruising, or persistent dizziness, treat it with more urgency than you otherwise might.
What Happens at the Emergency Room
Doctors can’t always diagnose internal bleeding from symptoms alone, so they rely on imaging. One of the first tools used in a trauma setting is a bedside ultrasound that checks four areas where blood tends to pool: the space around the heart, the upper right and upper left abdomen near the diaphragm, and the pelvis. This scan takes only a few minutes and can confirm whether free fluid (usually blood) is collecting where it shouldn’t be.
If the ultrasound suggests bleeding or your symptoms warrant further investigation, a CT scan provides a more detailed picture. Blood tests measuring your red blood cell count and clotting ability help determine how much blood you’ve lost and how quickly. In some cases, doctors use angiography, which involves injecting dye into blood vessels to pinpoint the exact source of bleeding.
Red Flags That Need Immediate Attention
Some combinations of symptoms should send you to the emergency room without hesitation:
- After a head injury: a worsening headache, vomiting, unequal pupils, confusion, or loss of consciousness
- After abdominal trauma: increasing belly pain or swelling, dizziness when standing, or visible bruising around the navel or flanks
- Without obvious injury: black or bloody stool paired with lightheadedness, rapid heartbeat, or pale and clammy skin
- On blood thinners: any of the above symptoms, even if they seem mild
Internal bleeding can progress from manageable to life-threatening quickly. The body’s ability to compensate for blood loss masks the severity for a while, which means by the time symptoms become obvious, you may have already lost a significant amount of blood. Acting on early, subtle signs gives doctors the best chance to find and stop the source before complications set in.