Hypotension, or low blood pressure, can result from a wide range of physiological and pathological conditions. While some individuals naturally have lower-than-average blood pressure with no adverse effects, others may experience serious symptoms when their pressure falls too low. Understanding the causes of hypotension is essential to determining whether the condition is benign, transient, or a sign of an underlying health issue requiring intervention.
In this section, we explore the many causes of hypotension, focusing on the mechanisms involved, the role of chronic diseases, medications, and situational triggers. Whether it occurs occasionally or persists over time, recognising the root cause is the first step towards effective management.
Primary Categories of Hypotension Causes
The causes of hypotension are divided into several main groups:
- Physiological (Normal) Causes
- Dehydration and Fluid Loss
- Cardiovascular Causes
- Endocrine and Metabolic Conditions
- Medication-Induced Hypotension
- Neurological and Autonomic Disorders
- Severe Infections and Shock States
- Nutritional and Lifestyle Factors
1. Physiological (Normal) Hypotension
Some people, especially young adults and athletes, naturally have lower blood pressure without any problems. In these cases, hypotension is a normal body variation. Their hearts and blood vessels work more efficiently. This means their heart pumps blood with less effort, so their blood pressure reads lower.
This type of hypotension does not usually need treatment. However, if symptoms like tiredness or dizziness appear, a doctor should check to rule out other causes.
2. Dehydration and Fluid Loss
Dehydration causes hypotension often. When the body loses more water than it takes in, blood volume drops. This happens through heavy sweating, vomiting, diarrhoea, or not drinking enough water. Lower blood volume means less pressure in the blood vessels.
For example, heat illnesses like heat exhaustion or heatstroke often cause dehydration-induced hypotension. Also, using too many water pills (diuretics) for health or weight loss can drain fluids quickly.
Children and older adults with severe diarrhoea or vomiting lose fluids fast. Without quick fluid replacement, their blood pressure can drop dangerously.
Causes of Hypotension in Heart Conditions
Several heart problems affect blood pressure control. These include:
- Bradycardia: A slow heart rate means the heart can’t pump enough blood.
- Heart failure: A weak heart muscle cannot push blood well.
- Heart valve problems: Faulty valves block or reduce blood flow.
- Heart attacks: Sudden damage to the heart lowers output.
- Irregular heartbeats (arrhythmias), like atrial fibrillation or heart block, disturb blood flow.
When these happen, hypotension often signals a serious or unstable problem needing quick care.
4. Endocrine and Metabolic Conditions
Hormones control blood pressure. When hormone systems fail, hypotension can occur. This happens because blood vessels relax too much, blood volume drops, or the heart weakens. Common hormone-related causes include:
- Addison’s disease: The adrenal glands do not make enough cortisol and aldosterone, which keep blood pressure steady.
- Hypothyroidism: Low thyroid hormone slows the heart and weakens contractions, causing low pressure.
- Diabetes: Long-term diabetes can damage nerves controlling blood vessel tightness, causing low pressure when standing.
- Low blood sugar (hypoglycaemia): In diabetic people, this can cause sudden blood pressure drops.
These problems often come with tiredness, weight loss, dizziness, or salt cravings.
5. Medication-Induced Hypotension
Many drugs lower blood pressure as a side effect or goal. Older adults taking many medicines (polypharmacy) face this risk more. Some examples are:
- Diuretics: They make you urinate more and lose blood volume.
- Beta-blockers and calcium blockers: These slow the heart and reduce strength.
- ACE inhibitors and ARBs: They widen blood vessels to lower pressure.
- Nitrates: Used for chest pain, they relax vessels but may drop pressure a lot.
- Certain antidepressants (tricyclics, MAOIs) can cause blood pressure to fall when standing.
- Erectile dysfunction drugs like sildenafil (Viagra) can dangerously lower pressure if combined with nitrates.
If medicines cause hypotension, doctors can adjust doses or change drugs.
6. Neurological and Autonomic Disorders
The autonomic nervous system controls automatic body functions like heart rate and blood pressure. Damage here can stop vessels from tightening properly. This leads to low blood pressure, especially when standing. Doctors call this autonomic failure or neurogenic orthostatic hypotension.
Conditions causing this include:
- Parkinson’s disease
- Multiple system atrophy (MSA)
- Diabetic nerve damage
- Spinal cord injury
- Shy-Drager syndrome
People with these often feel dizzy, see spots, or faint when they stand up.
7. Severe Infections and Shock States
Shock causes blood pressure to fall very low, putting organs at risk. It can happen from:
- Sepsis: A serious infection causing body-wide inflammation and vessel widening.
- Anaphylaxis: A fast allergic reaction dropping pressure dangerously.
- Severe blood loss from injury or surgery.
- Heart failure causing cardiogenic shock.
- Spinal injury causing neurogenic shock.
All these need emergency care and can be deadly if not treated quickly.
8. Nutritional and Lifestyle Factors
What you eat and how you live affect blood pressure. For example:
- Low salt diets can lower pressure too much in some people.
- Drinking too much alcohol causes dehydration and vessel widening, both lower pressure.
- Poor nutrition, especially lacking vitamin B12, folate, or iron, lowers blood production and pressure.
- Long bed rest or little activity weakens the heart and vessels, making pressure regulation poor.
These causes of hypotension can often improve with better diet, drinking enough water, and more exercise.
Conclusion
The causes of hypotension are many and range from harmless body differences to serious emergencies. To find the exact cause, doctors check symptoms, health history, medicines, and may do tests. While many cases are easy to treat, some need long-term care or urgent help. Knowing the signs early and what causes hypotension helps ensure fast, proper treatment.
