From the Guidelines

Blood pressure does not typically decrease when one is ill, and hypotension is not a common presentation in acute illness.

In fact, studies suggest that blood pressure at presentation might be higher in patients who go on to develop more severe illness, independent of the presence of baseline hypertension 1.
The renin-angiotensin system (RAS) is upregulated in acute illness to maintain adequate organ perfusion, which can lead to increased blood pressure 1.
However, in some cases, such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, hypotension can occur due to multi-organ dysfunction, but this is uncommon at presentation 1.

The management of blood pressure in acute illness is complex and depends on various factors, including the underlying cause of the illness, the presence of comorbidities, and the patient's overall clinical condition.
In the context of acute ischemic stroke, the American Heart Association recommends cautious management of blood pressure, with a goal of lowering blood pressure by 15% to 25% within the first day, unless the diastolic blood pressure is 120 mm Hg or the systolic blood pressure is 220 mm Hg 1.
Rapid and steep reductions in blood pressure may be harmful, and the consensus is to withhold emergency administration of antihypertensive agents unless necessary 1.

From the Research

Blood pressure is a critical factor in maintaining organ perfusion, and hypotension can lead to organ dysfunction and morbidity 2.
Hypotension is a common phenomenon in clinical practice, and it can be divided into two categories: chronic constitutional hypotension and hypotension associated with abnormal postural control 3.
The causes of hypotension are varied and can include autonomic neuropathies, baroreceptor dysfunction, and hypovolemia 4.

When one is ill, blood pressure can decrease, leading to hypotension 3, 4.
Hypotension can be a causative mechanism in patients with chronic fatigue syndrome 3.
In critically ill patients, hypotension is common and can be associated with organ dysfunction and mortality 2, 5.

Diagnosis of hypotension can be problematic, and ambulatory blood pressure monitoring may be a more reliable method for determining mean blood pressure levels and identifying episodes of marked hypotension 3.
Treatment of hypotension depends on the underlying cause and can include medication, fluid replacement, and other interventions 4.
Predicting hypotension before it becomes clinically apparent can allow for pre-emptive treatment and reduce the severity and duration of hypotension 2.