Whether you should temporarily stop your blood pressure medication depends on the specific situation: an upcoming surgery, an acute illness with vomiting or dehydration, or symptoms suggesting your blood pressure is dropping too low. The answer also varies by which medication you take, because some are dangerous to stop abruptly while others are routinely paused. Here’s what matters for each scenario.
Before Surgery: Which Medications to Hold
Surgery is the most common reason blood pressure medications get temporarily paused, and the rules differ sharply depending on which drug you’re on. The core concern is that anesthesia lowers blood pressure on its own, and certain medications can amplify that drop to dangerous levels.
ACE Inhibitors and ARBs
These are the medications most consistently recommended to pause before surgery. The European Society of Cardiology’s 2022 guidelines recommend withholding them in patients with high blood pressure who don’t have heart failure. The Canadian Cardiovascular Society similarly advises stopping them on the day of surgery. A 2022 consensus statement from the Society for Perioperative Assessment and Quality Improvement recommends holding them the morning of surgery but notes that continuing may be acceptable for low-risk procedures. For people with chronic kidney disease, the 2024 KDIGO guideline suggests considering a longer pause of 48 to 72 hours before elective surgery.
One important exception: if you take these medications for heart failure rather than just high blood pressure, the calculus shifts. The American College of Cardiology and American Heart Association have noted it may be reasonable to continue them in heart failure patients to maintain cardiovascular stability. Your surgical team will make this call based on your specific situation.
Beta-Blockers: Do Not Stop Abruptly
Beta-blockers are one medication you should almost always continue on the morning of surgery. Stopping them suddenly, even for a single day, can trigger a rebound effect: your heart rate spikes, cardiac demand increases, and the risk of dangerous heart rhythms goes up. In patients undergoing surgery, skipping beta-blockers on the day of the procedure alone was associated with roughly double the odds of a serious cardiac event within 90 days. Beta-blocker withdrawal has also been linked to higher in-hospital and one-year mortality in vascular surgery patients. Take your beta-blocker with a small sip of water the morning of surgery unless your surgical team specifically tells you otherwise.
Calcium Channel Blockers
Like beta-blockers, calcium channel blockers should generally be continued on the morning of surgery. They don’t carry the same rebound risk, but maintaining them helps keep blood pressure stable through the stress of the procedure.
Diuretics
Water pills are typically held the morning of surgery. Since you’ll be fasting and unable to drink fluids freely, taking a diuretic increases the risk of dehydration, low blood pressure under anesthesia, and electrolyte imbalances. Your surgeon or anesthesiologist will tell you when to restart them.
Clonidine: Another One to Never Stop Suddenly
If you take clonidine (a centrally acting blood pressure medication), do not skip it before surgery without guidance. Abruptly stopping clonidine can cause a dramatic rebound in both heart rate and blood pressure, typically appearing 12 to 60 hours after the last dose. In studies, nearly all patients who suddenly stopped clonidine experienced excessive spikes in heart rate and blood pressure, and about half developed symptoms severe enough to need treatment. This rebound is driven by a surge in the sympathetic nervous system, essentially your body’s fight-or-flight response going into overdrive.
During Illness: The “Sick Day” Rules
When you’re dealing with vomiting, diarrhea, high fevers, or anything that makes you unable to keep fluids down, several blood pressure medications become temporarily risky. The problem isn’t the medication itself but how it interacts with dehydration. When your body is already low on fluid, drugs that lower blood pressure or increase urine output can push you toward dangerously low blood pressure, kidney injury, or electrolyte problems.
The medications to consider pausing during a dehydrating illness include diuretics (which worsen fluid loss), ACE inhibitors and ARBs (which can impair the kidneys’ ability to maintain blood flow when you’re dehydrated, raising the risk of acute kidney injury), and any combination of these. Australian clinical guidelines advise patients to stop these medications during episodes of diarrhea, vomiting, low blood pressure, or major infection, and to wait until they are “clearly improving” before restarting.
The key symptoms that signal you may be at risk: inability to eat, diarrhea, vomiting, and fever with sweating or chills. If you experience these and take blood pressure medications, checking in with your prescribing provider about a temporary pause is a reasonable step. For short illnesses lasting a day or two, missing a dose or two of a diuretic or ACE inhibitor is generally far safer than taking them while severely dehydrated.
Low Blood Pressure Symptoms to Watch For
Sometimes the reason to hold a dose is simply that your blood pressure is already too low. This is especially relevant for older adults, people on multiple blood pressure medications, or anyone who has recently had a dose increase. Orthostatic hypotension, a drop in blood pressure when you stand up, is a common sign that your medication may be doing too much. The clinical threshold is a drop of 20 mmHg or more in systolic pressure (the top number) or 10 mmHg or more in diastolic pressure (the bottom number) when moving from sitting to standing. Lightheadedness or dizziness on standing also qualifies even if the numbers don’t hit those cutoffs.
If you’re checking your blood pressure at home and consistently seeing readings below 90/60, or you’re feeling dizzy, lightheaded, or faint, it’s worth contacting your provider about whether to skip a dose. This is different from a one-time low reading, which can happen after a hot bath, a big meal, or mild dehydration.
When Low Blood Pressure Becomes an Emergency
On the flip side, you should know the difference between blood pressure that’s simply too high (which may prompt a medication adjustment) and a hypertensive emergency. A reading above 180/120 without symptoms like chest pain, vision changes, or shortness of breath is considered hypertensive urgency. It’s serious but typically managed with oral medications over hours to days. You wouldn’t hold medication in this situation; you’d likely take it.
A reading above 180/120 with symptoms like severe headache, visual disturbances, chest pain, difficulty breathing, confusion, or seizures is a hypertensive emergency. This involves active organ damage and requires hospital-level care, not a medication adjustment at home.
Restarting After Surgery
The 2024 AHA/ACC guidelines are clear that blood pressure medications taken chronically should be restarted as soon as clinically reasonable after surgery to prevent complications from uncontrolled postoperative hypertension. In practice, “as soon as reasonable” means when you can swallow pills and your blood pressure is stable enough to tolerate them.
This transition isn’t always smooth. In one study of patients recovering from hip or knee replacement, 35% experienced a drop in blood pressure after their medications were restarted. Patients who had already had a low blood pressure episode before restarting were at even higher risk, with 42% experiencing another drop. This is why nursing teams typically check your blood pressure before handing you your home medications in the hospital. If you’re recovering at home and unsure about restarting, checking your blood pressure before taking a dose gives you useful information to share with your provider.
For beta-blockers and clonidine specifically, the goal is to resume as quickly as possible given the rebound risks described above. If you can’t take pills by mouth after surgery, your medical team can use intravenous alternatives to bridge the gap.