A hypertensive crisis occurs when blood pressure spikes above 180/120 mm Hg, a level high enough to damage organs within hours. The causes range from missed blood pressure medications and kidney disease to drug use and rare tumors, but they all share a common thread: something overwhelms the body’s ability to regulate pressure in the blood vessels.
What Happens Inside the Body
Your blood vessels are lined with a thin layer of cells that constantly produce a molecule called nitric oxide. This molecule relaxes the muscular walls of arteries, keeping them open and flexible. Under normal conditions, there’s a balance between signals that widen blood vessels and signals that constrict them.
During a hypertensive crisis, that balance collapses. Oxidative stress, essentially an overload of harmful molecules called free radicals, destroys nitric oxide before it can do its job. Worse, the enzyme that normally produces nitric oxide starts malfunctioning and generates more free radicals instead. The result is a vicious cycle: blood vessels clamp down, pressure climbs further, and the rising pressure damages the vessel lining even more, which produces still more free radicals. This is why a hypertensive crisis can escalate so quickly once it begins.
Urgency vs. Emergency: Why the Difference Matters
Not every hypertensive crisis is the same. The 2025 AHA/ACC guidelines draw a sharp line between two categories, and the distinction isn’t based on how high the numbers go. It’s based on whether your organs are being actively harmed.
A hypertensive emergency means blood pressure above 180/120 mm Hg with signs of acute organ damage. That can show up as sudden confusion or vision changes (from brain swelling), chest pain (from the heart being overworked), severe shortness of breath (from fluid backing up into the lungs), or rapidly worsening kidney function. An aortic dissection, where the wall of the body’s largest artery tears, is the least common but most dangerous presentation.
When blood pressure is above 180/120 but there’s no organ damage, the guidelines now call this “severe hypertension” rather than the older term “hypertensive urgency.” It still needs treatment, but the approach is less aggressive: adjusting oral medications rather than emergency intervention.
Skipping or Stopping Blood Pressure Medication
The single most common trigger for a hypertensive crisis in people who already have high blood pressure is not taking their medication as prescribed. This includes forgetting doses, running out of refills, or intentionally stopping because they feel fine. Some medications, particularly certain older classes of blood pressure drugs, can cause a rebound effect when stopped abruptly. Blood pressure doesn’t just return to where it was before treatment. It can spike well above those levels, sometimes within 24 to 48 hours.
Kidney Disease and Artery Narrowing
The kidneys are central to blood pressure regulation. They control how much salt and water your body retains, and they release hormones that tighten or relax blood vessels. When kidney function declines, the body holds onto extra fluid, and blood pressure rises. That elevated pressure then damages the kidneys further, creating a feedback loop that can spiral into crisis.
Narrowing of the arteries that supply the kidneys, a condition called renal artery stenosis, can trigger the same cascade even when the kidneys themselves started out healthy. The restricted blood flow tricks the kidneys into thinking blood pressure is too low, so they release hormones that raise it aggressively. This is one of the more common causes of hypertensive crisis in people who’ve never been diagnosed with high blood pressure before.
Cocaine and Other Stimulant Drugs
Cocaine is the most common illicit drug associated with life-threatening cardiovascular emergencies, including hypertensive crisis. It works by flooding the nervous system with signals that constrict blood vessels and accelerate the heart. The spike is rapid and intense, and it can trigger stroke, heart attack, or aortic dissection even in otherwise healthy young adults.
Amphetamines, methamphetamine, and even high doses of certain over-the-counter decongestants that mimic adrenaline can produce similar effects. The risk is highest in people who already have undiagnosed or untreated high blood pressure, because their baseline is already elevated before the drug pushes it further.
Adrenal Gland Tumors
A pheochromocytoma is a rare tumor that grows in the adrenal glands, which sit on top of the kidneys. These tumors produce surges of adrenaline and related hormones at unpredictable times, causing sudden episodes of dangerously high blood pressure, rapid heartbeat, sweating, and headache. The episodes can be triggered by physical exertion, certain foods, or even just changing body position. Between episodes, blood pressure may be completely normal, which is why pheochromocytomas are frequently missed for years.
Other endocrine conditions, including an overactive thyroid and disorders that cause excess production of the hormone aldosterone, can also push blood pressure to crisis levels, though they more commonly cause sustained high blood pressure that gradually worsens.
Pregnancy Complications
Preeclampsia is a pregnancy-specific condition diagnosed when blood pressure reaches 140/90 mm Hg or higher after 20 weeks of gestation, along with protein in the urine. It can progress rapidly to severely elevated pressures that qualify as a hypertensive emergency, with risks including seizures (eclampsia), liver damage, and stroke.
Several factors raise the likelihood of preeclampsia: a first pregnancy, carrying twins or triplets, obesity, and pre-existing conditions like high blood pressure, diabetes, or kidney disease. A family history of preeclampsia also increases risk. The condition resolves after delivery, but the blood pressure crisis it causes in the meantime can be immediately dangerous for both the mother and the baby.
Food and Drug Interactions With MAOIs
A lesser-known but well-documented cause involves a class of antidepressants called MAOIs (monoamine oxidase inhibitors). These medications block an enzyme that normally breaks down a substance called tyramine in your body. When someone on an MAOI eats foods high in tyramine, the compound builds up rapidly and triggers a sudden, severe blood pressure spike.
Foods that are high in tyramine include:
- Aged and artisan cheeses: cheddar, Swiss, Parmesan, blue cheeses like Stilton and Gorgonzola, brie, Camembert, feta, Gruyere, and Edam
- Cured and processed meats: pepperoni, salami, dry sausages, bologna, bacon, corned beef, and smoked fish
- Fermented and pickled foods: sauerkraut, kimchi, pickles, caviar, tofu, and pickled fish
- Fermented beverages: kombucha and kefir
People prescribed MAOIs are given strict dietary guidance, but accidental exposure still causes emergency room visits. The reaction can come on fast, sometimes within minutes of eating a triggering food.
Other Contributing Triggers
Several additional situations can push blood pressure into crisis territory. Severe pain, panic attacks, and extreme emotional stress all activate the sympathetic nervous system and raise blood pressure sharply, though they rarely cause sustained crisis-level readings on their own. Certain autoimmune conditions that inflame blood vessels, head injuries, and spinal cord injuries can also trigger dangerously high blood pressure.
In some cases, a hypertensive crisis has no single identifiable cause. A person with long-standing, poorly controlled high blood pressure may gradually lose the ability of their blood vessels to self-regulate. At that point, even a minor stressor, a missed dose, a salty meal, a stressful day, can be enough to tip the system past its breaking point.