Brief Answer:
Multiple causes, explained

Detailed Answer:
Thank you for asking!
Hypotension / Low blood pressure has multiple causes and all of them need to be managed accordingly.
Here are some of the causes for low blood pressure.
Getting up after you sit or lie down. This can cause a quick drop in blood pressure called orthostatic hypotension.
Standing for a long time.
Not drinking enough fluids (dehydration).When you become dehydrated, your body loses more water than it takes in. Even mild dehydration can cause weakness, dizziness and fatigue. Fever, vomiting, severe diarrhea, overuse of diuretics and strenuous exercise can all lead to dehydration.

Far more serious is hypovolemic shock, a life-threatening complication of dehydration. It occurs when low blood volume causes a sudden drop in blood pressure and a reduction in the amount of oxygen reaching your tissues. If untreated, severe hypovolemic shock can cause death within a few minutes or hours.
Medicines, such as high blood pressure medicine or other heart medicines.
Health problems such as thyroid disease, severe infection, bleeding in the intestines, or heart problems.
Trauma, such as major bleeding or severe burns. Losing a lot of blood from a major injury or internal bleeding reduces the amount of blood in your body, leading to a severe drop in blood pressure.
Endocrine problems like addison's disease, hypoglycemia, parathyroid disease and diabetes in some cases can trigger hypotension.
In pregnancy it drops too Because a woman's circulatory system expands rapidly during pregnancy, blood pressure is likely to drop. This is normal, and blood pressure usually returns to your pre-pregnancy level after you've given birth.
Some heart conditions that can lead to low blood pressure include extremely low heart rate (bradycardia), heart valve problems, heart attack and heart failure
Septicemia can happen when an infection in the body enters the bloodstream. This condition can lead to a life-threatening drop in blood pressure called septic shock.
Severe allergic reaction (anaphylaxis). Anaphylaxis is a severe and potentially life-threatening allergic reaction. Common triggers of anaphylaxis include foods, certain medications, insect venoms and latex. Anaphylaxis can cause breathing problems, hives, itching, a swollen throat and a drop in blood pressure.
Lack of nutrients in your diet. A lack of the vitamins B-12 and folate can cause a condition in which your body doesn't produce enough red blood cells (anemia), causing low blood pressure.
There are many medicines which can cause low blood pressure like
Diuretics (water pills), such as furosemide (Lasix) and hydrochlorothiazide (Microzide, Oretic)
Alpha blockers, such as prazosin (Minipress) and labetalol
Beta blockers, such as atenolol (Tenormin), propranolol (Inderal, Innopran XL, others) and timolol
Drugs for Parkinson's disease, such as pramipexole (Mirapex) or those containing levodopa
Certain types of antidepressants (tricyclic antidepressants), including doxepin (Silenor), imipramine (Tofranil), protriptyline (Vivactil) and trimipramine (Surmontil)
Sildenafil (Viagra) or tadalafil (Cialis), particularly in combination with the heart medication nitroglycerin
I hope you see the wide array of possibilities for the hypotension now.
To check for the causes of your low blood pressure, your doctor will ask about your past health, your symptoms, and the medicines you take. He or she will do a physical exam and may do other tests. Your doctor may check for another health problem that could be causing your low blood pressure.
Seek a cardiologist and let them help you with the hypotension.
I hope it helps. Don't forget to close the discussion please.
Take care
Regards
S Khan

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