What Could Be Causing Your Low Blood Pressure? Ten Possibilities

Heart conditions that limit blood flow — such as arrhythmias, heart failure, valve disorders, or recent heart attacks — can cause a dangerous drop in blood pressure. When the heart can’t pump blood effectively, organs and tissues don’t get the oxygen they need. In some cases, abnormal rhythms (arrhythmias) disrupt the heart’s ability to circulate blood entirely, leading to fainting or shock.

Dehydration doesn’t just make you thirsty — it lowers your blood volume, which can lead to low blood pressure. Common triggers include illness (like fever or vomiting), strenuous activity, or not drinking enough water. Fatigue, lightheadedness, and dry mouth may be early warning signs.

Severe infections can cause a life-threatening drop in blood pressure, especially if they enter the bloodstream. This condition, known as septic shock, leads to widespread inflammation and dangerously low pressure. If you have an infection and start feeling weak, feverish, or dizzy, seek urgent medical care.

A severe allergic reaction (anaphylaxis) can cause blood vessels to widen and blood pressure to plummet. Common triggers include insect stings, shellfish, nuts, and latex. Symptoms include swelling, difficulty breathing, and confusion. If you suspect anaphylaxis, use an epinephrine injector and call emergency services immediately.

Deficiencies in key nutrients — especially vitamin B12, folate, and iron — can cause anemia, which in turn may lower blood pressure. These nutrients help your body produce red blood cells. Without enough of them, your circulation slows and symptoms like fatigue and lightheadedness may develop.

It’s common for blood pressure to drop during the first and second trimesters of pregnancy. This is largely due to hormonal changes and the rapid expansion of the circulatory system. While typically harmless, low pressure during pregnancy can sometimes signal a problem, especially if it’s accompanied by dizziness, vision changes, or fainting. In rare cases, it may indicate placental issues and should be evaluated by a doctor.

Hormonal disorders can interfere with blood pressure regulation. Conditions like hypothyroidism, adrenal insufficiency (Addison’s disease), or low blood sugar (hypoglycemia) may cause sudden or chronic drops in blood pressure. Diabetes can also damage the nerves that help regulate blood pressure, especially in older adults.

A number of medications can lower blood pressure as a side effect — sometimes too much. These include diuretics, beta-blockers, certain antidepressants, erectile dysfunction drugs, and medications used to treat high blood pressure itself. Taking multiple medications or mixing drug classes may compound the effect.

Older adults are more likely to experience low blood pressure, especially when standing up quickly — a condition called orthostatic hypotension. Age-related diseases like Parkinson’s, diabetes, and nerve disorders can disrupt the body’s ability to regulate pressure. Some older individuals also develop post-meal hypotension, where blood pressure drops after eating.

Spending too long in hot weather or direct sun can lead to heat exhaustion, especially if you’re not hydrated. As your body loses fluid, blood volume drops, which can cause dizziness or even fainting. If left untreated, this can escalate to heat stroke — a medical emergency that affects multiple organ systems and requires immediate care.