Blood donation eligibility is governed by strict safety protocols designed to protect both the recipient and the donor. Uncontrolled high blood pressure (hypertension) is a sustained elevation in the force of blood against the artery walls. If not managed, this condition increases the risk of adverse health events, which can be exacerbated by the physiological stress of donating blood. Deferral is a temporary measure intended to safeguard the donor’s health during and immediately after the procedure.
The Specific Blood Pressure Limits for Donors
Blood collection centers require donors to meet specific numerical thresholds on the day of donation. The systolic reading (the top number, measuring pressure during a heartbeat) must be no higher than 180 millimeters of mercury (mmHg). The diastolic reading (the bottom number, measuring pressure between heartbeats) must be no higher than 100 mmHg.
A minimum reading is also required to ensure the donor is not hypotensive, which could cause complications. Systolic pressure must be at least 90 mmHg, and diastolic pressure must be at least 50 mmHg. If a reading falls outside of this acceptable range, the donor will be deferred until their blood pressure is stable.
Why Donation Poses a Risk to the Donor with Uncontrolled HBP
The primary reason for deferral is the physiological stress caused by the rapid loss of blood volume during donation. A standard whole blood donation removes about one pint, creating an acute, temporary state of reduced blood volume called hypovolemia. In a healthy person, the body’s baroreceptor reflex quickly compensates by narrowing blood vessels and slightly increasing the heart rate to maintain pressure.
However, in someone with uncontrolled hypertension, this compensatory mechanism may be compromised or strained. High blood pressure often indicates underlying cardiovascular stiffness and reduced vascular compliance. This means the blood vessels cannot easily constrict to counteract the sudden drop in volume, making the donor susceptible to a severe, rapid drop in blood pressure.
This sudden drop increases the likelihood of a vasovagal reaction, manifesting as severe dizziness, pallor, nausea, and fainting. An already overburdened heart, characteristic of uncontrolled high blood pressure, is forced to work harder to maintain circulation with less fluid volume. Though rare, the added workload and pressure fluctuations can increase the risk of an acute cardiovascular event, such as a stroke or heart attack, during or immediately following the procedure.
The Role of Medication in Determining Eligibility
Taking medication to manage hypertension does not automatically disqualify an individual from donating blood. Eligibility focuses on the resulting blood pressure reading at the time of screening, not the mere presence of a prescription. Many common blood pressure medications, including ACE inhibitors, beta-blockers, and diuretics, are acceptable for blood donors.
As long as the medication successfully keeps the systolic and diastolic readings within the acceptable limits, the donor is eligible. However, if a donor has recently started a new hypertension medication or had a change in dosage, some centers may require a waiting period. This temporary deferral, often around four weeks, ensures the medication’s effect is stable and the body is well-adjusted before the stress of donation.
Becoming Eligible: Donating with Controlled Hypertension
For individuals deferred due to elevated blood pressure, the path to eligibility centers on establishing stable, controlled hypertension. The deferral should prompt consultation with a healthcare provider about the high reading. Consistent monitoring and adherence to any prescribed treatment plan are the most effective steps to becoming eligible again.
Once a donor’s blood pressure is consistently within the range of 90/50 mmHg to 180/100 mmHg, they are welcome to attempt donation again. The goal is to ensure the cardiovascular system is not under undue stress, allowing the body to safely manage the temporary blood volume loss. By successfully managing their hypertension, potential donors protect their own health while opening the door to helping others.