Understanding Blood Pressure Readings
Blood pressure is the force of blood pushing against the walls of your arteries. It is measured in millimeters of mercury (mmHg) and consists of two numbers: systolic and diastolic.
- Systolic pressure: The top number, which measures the pressure in your arteries when your heart beats and pumps blood.
- Diastolic pressure: The bottom number, which measures the pressure in your arteries when your heart is at rest between beats.
A typical, healthy blood pressure reading for most adults is below 120/80 mmHg. The numbers fluctuate throughout the day based on various factors like stress, physical activity, and diet. However, a consistently low reading can indicate hypotension, especially if accompanied by symptoms.
What is Considered Low mmHg?
Medically, what is considered low mmHg is a blood pressure reading below 90/60 mmHg. It is important to note that what is considered low for one person might be normal for another. Some people, particularly those who are very physically active or young, may have blood pressure that consistently falls within this range without causing any health issues. The concern arises when blood pressure drops suddenly or if it is consistently low and accompanied by noticeable symptoms. A sudden drop of just 20 mmHg in systolic pressure, for example, from 110 to 90 mmHg, can cause immediate symptoms like dizziness.
Symptoms and Causes of Low Blood Pressure
Symptoms of low blood pressure can be mild or severe, and they often indicate that vital organs, like the brain, are not receiving enough blood flow. It's crucial to identify the root cause to determine the appropriate course of action.
Common symptoms of hypotension:
- Dizziness or lightheadedness, especially when standing up
- Fainting (syncope)
- Blurred or fading vision
- Nausea or vomiting
- Fatigue or weakness
- Lack of concentration
- Cold, clammy, or pale skin
- Rapid, shallow breathing
- Weak and rapid pulse
Potential causes of low blood pressure:
- Dehydration: Not drinking enough fluids can decrease blood volume, causing blood pressure to drop. This can be exacerbated by fever, vomiting, or strenuous exercise.
- Pregnancy: The circulatory system expands rapidly to support the fetus, often causing a drop in blood pressure during the first and second trimesters. It typically returns to normal after childbirth.
- Heart conditions: A heart attack, heart failure, heart valve disease, or a slow heart rate (bradycardia) can affect the heart's ability to pump blood efficiently, leading to low pressure.
- Endocrine problems: Conditions like thyroid disease, adrenal insufficiency (Addison's disease), or low blood sugar (hypoglycemia) can trigger hypotension.
- Severe infection (septic shock): An infection that enters the bloodstream can lead to a life-threatening drop in blood pressure.
- Severe allergic reaction (anaphylaxis): This can lead to a sudden and significant drop in blood pressure.
- Medications: Certain medications, including those used for high blood pressure, diuretics, antidepressants, and treatments for Parkinson's disease, can have low blood pressure as a side effect.
- Nutritional deficiencies: A lack of essential nutrients like vitamin B-12, folate, or iron can lead to anemia and subsequently, low blood pressure.
- Blood loss: Losing a significant amount of blood from an injury or internal bleeding reduces blood volume and causes a severe drop in blood pressure.
Types of Hypotension
Health professionals often categorize low blood pressure into different types based on the cause and timing of the blood pressure drop.
- Orthostatic (postural) hypotension: A sudden drop in blood pressure when you stand up from a sitting or lying position. This is caused by gravity pooling blood in your legs and the body's failure to compensate by constricting blood vessels. It is more common in older adults but can happen to anyone.
- Postprandial hypotension: A drop in blood pressure that occurs one to two hours after eating. It is thought to happen because of increased blood flow to the digestive tract. It is most common in older adults, especially those with high blood pressure or certain nervous system disorders like Parkinson's disease.
- Neurally mediated hypotension: A drop in blood pressure that happens after standing for long periods. It is more common in young adults and children and is thought to result from miscommunication between the heart and the brain.
Comparison: Normal vs. Low Blood Pressure
| Feature | Normal Blood Pressure | Low Blood Pressure (Hypotension) |
|---|---|---|
| Systolic (Top Number) | Less than 120 mmHg | Less than 90 mmHg |
| Diastolic (Bottom Number) | Less than 80 mmHg | Less than 60 mmHg |
| Symptom Presence | Typically none | Can cause dizziness, fainting, fatigue, etc., especially if sudden |
| Impact on Body | Healthy circulation to all organs | Reduced blood flow to organs, potentially leading to damage in severe cases |
| Medical Concern | Not a concern | Only a concern if symptomatic or a sudden, severe drop occurs |
Treatment and When to Seek Help
Treatment for low blood pressure depends entirely on the underlying cause. If you have consistently low readings but feel fine, treatment may not be necessary, though your doctor may want to monitor your condition during routine exams. However, if symptoms are present or if the drop is sudden and severe, intervention is needed.
Treatment options:
- Lifestyle changes: These can include increasing salt and fluid intake (under a doctor's supervision), wearing compression stockings to reduce blood pooling in the legs, and eating smaller, low-carbohydrate meals to prevent postprandial drops.
- Medication adjustments: If a medication is causing the low blood pressure, your doctor may change the dosage or switch you to a different drug.
- Medications for hypotension: In severe cases, specific medications like fludrocortisone or midodrine may be prescribed to increase blood pressure.
- IV fluids: For acute dehydration or shock, intravenous (IV) fluids may be administered to increase blood volume.
- Treating the underlying condition: If low blood pressure is caused by an underlying condition, such as an infection or heart problem, treating that condition will often resolve the hypotension.
When to seek immediate medical attention:
You should seek immediate medical help if you experience signs of shock, which include cold, clammy, or pale skin; rapid, shallow breathing; or a weak, rapid pulse. These are signs that your body's vital organs are not receiving enough blood and oxygen. Other symptoms warranting a call to your doctor include persistent dizziness, fainting, chest pain, or an irregular heartbeat.
Conclusion
Understanding what is considered low mmHg is a crucial part of managing your cardiovascular health, but it's important to consider more than just the numbers. While a reading below 90/60 mmHg is medically defined as hypotension, a low reading is only a concern when it is symptomatic. Regular monitoring, knowing the signs of trouble, and discussing any concerns with a healthcare provider are the best ways to ensure your blood pressure is at a healthy level for you. By proactively managing your health, you can address potential issues before they become serious.
For more detailed information on cardiovascular health, you can refer to the American Heart Association.
