Yes, in most cases you should temporarily hold ACE inhibitors and ARBs (like lisinopril and losartan) during a dehydrating illness with two or more episodes of vomiting or diarrhea. This is a short pause, not a permanent stop. You restart once you have eaten and drunk normally for 24 to 48 hours. Always confirm the plan with your doctor or pharmacist first.
Why a dehydrating illness changes the rules
On a normal day, your blood pressure pill is doing exactly what it should. The problem starts when a stomach bug, food poisoning, or a high fever dries you out.
When you lose fluid through vomiting, diarrhea, or heavy sweating, your blood volume drops. Your kidneys rely on a hormone called angiotensin II to protect themselves during these low-volume moments. ACE inhibitors and ARBs work by blocking that exact hormone, which is great for lowering blood pressure but unhelpful when you are dehydrated.
This is not a small detail. An international expert consensus published in the American Journal of Kidney Diseases agreed that renin-angiotensin system inhibitors (the group that includes ACE inhibitors and ARBs) should be temporarily stopped during an acute dehydrating illness. The reason is spelled out plainly in a clinical review on sick-day medication: "the normal physiological response to hypovolaemia is impaired by ACE inhibitors and sartans, patients taking these drugs are at increased risk of acute kidney injury."
Why these pills become a kidney risk when you are dry
Here is the mechanism in plain language. When your blood volume is low, angiotensin II tightens a tiny vessel leaving the kidney's filter (the efferent arteriole). That squeeze keeps enough pressure inside the filter to keep it working.
ACE inhibitors and ARBs relax that vessel. On a well-hydrated day, that is harmless. But when you are dehydrated, the filter loses the pressure it needs, kidney blood flow drops, and you can develop acute kidney injury. That is why the same pill that protects your heart for years can briefly turn risky during a bad stomach bug.
Even the patient label hints at the danger. The MedlinePlus page for lisinopril warns that "diarrhea, vomiting, not drinking enough fluids, and sweating a lot can cause a drop in blood pressure, which may cause lightheadedness and fainting."
Which blood pressure medications to pause (and which usually stay)
Not every blood pressure pill follows the same rule. The "pause when sick" advice mainly applies to drugs that affect your kidneys or fluid balance. Calcium channel blockers and beta-blockers usually continue, though you should never assume. Confirm your own list with your pharmacist.
| Medication type | Common examples | Sick-day plan |
|---|---|---|
| ACE inhibitors | lisinopril, ramipril, enalapril | Usually pause during a dehydrating illness (kidney risk) |
| ARBs | losartan, valsartan, olmesartan | Usually pause during a dehydrating illness (kidney risk) |
| Diuretics (water pills) | furosemide, hydrochlorothiazide | Often paused too, since they add to fluid loss. Ask your doctor. |
| Calcium channel blockers | amlodipine, diltiazem | Usually continue, but confirm with your pharmacist |
| Beta-blockers | metoprolol, propranolol | Usually continue and should not be stopped suddenly |
If you also take a water pill, read more about what happens when you stop blood pressure medication so you can tell a short sick-day pause apart from a permanent stop.
A simple sick-day plan for ACE inhibitors and ARBs
You do not need to memorize a medical textbook. You need a short, clear plan.
Step 1: Spot a true dehydrating illness
The trigger is not a mild sniffle. It is two or more episodes of vomiting or diarrhea, a high fever with heavy sweating, or being unable to keep fluids down. A single loose stool is not the same as a dehydrating illness.
Step 2: Hold the dose and sip fluids
Skip your ACE inhibitor or ARB at the first clear sign you cannot keep food or fluids down, then call or message your prescriber. Take small, frequent sips of water or an oral rehydration drink. This is the same pause approach used in the sick-day guidance reviewed in the literature, where these medicines are withheld during the illness and resumed once you recover.
Step 3: Restart when you are clearly better
Restart your medication after you have been eating and drinking normally again, usually for 24 to 48 hours. Do not take extra pills to "make up" for the doses you skipped. If you are unsure, your pharmacist can confirm the timing for your specific medication.
This pause-and-restart pattern is the same idea behind the Jardiance sick-day rules and the metformin sick-day rules, but the reason differs for each drug. Jardiance is paused to avoid a type of diabetic ketoacidosis, and metformin is paused to avoid lactic acidosis. For ACE inhibitors and ARBs, the concern is kidney injury from low blood flow.
When to skip the pause and get help now
A sick-day pause is for manageable illness at home. Some signs mean you need urgent care instead of a do-it-yourself plan. Seek medical help right away if you have more than four episodes of vomiting in 12 hours, cannot drink anything at all, feel confused or very drowsy, or feel faint with a very low blood pressure reading.
If your regular schedule already feels hard to track, our guides on the best time to take lisinopril and what to do after a missed dose of lisinopril can help you build a steadier routine once you are well. The same applies if you take an ARB, where a missed dose of losartan follows similar logic.
How Pillo helps you pause and restart safely
The hard part of a sick day is not pausing your pill. It is remembering to start again at the right time, especially when you are wiped out and the days blur together.
Pillo lets you pause a medication and set a reminder to restart it once you are back to normal. Its persistent alarm keeps nudging you until you confirm the dose, so a paused pill does not quietly disappear from your routine. If you manage medications for a parent or partner as a dependent, you can track their sick-day pause the same way, all from your own phone.
Frequently Asked Questions
Should I stop lisinopril if I have a stomach bug?
If the stomach bug causes two or more episodes of vomiting or diarrhea, most sick-day guidance says to temporarily hold lisinopril and call your prescriber. A mild upset stomach without real fluid loss is different. When in doubt, ask your doctor or pharmacist, since they know your full health picture.
How long should I hold my blood pressure medication when sick?
You generally hold it during the illness and restart after you have eaten and drunk normally for about 24 to 48 hours. The exact timing depends on how dehydrated you became and your other health conditions, so confirm the restart day with your pharmacist.
Is it dangerous to keep taking ACE inhibitors when dehydrated?
It can be. Because ACE inhibitors and ARBs block the hormone that protects your kidneys during low blood volume, taking them while badly dehydrated raises the risk of acute kidney injury. That is the main reason these drugs are paused during a dehydrating illness.
Do I need to stop all blood pressure medications when sick?
No. The pause mainly applies to ACE inhibitors, ARBs, and often diuretics, which affect fluid and kidney function. Calcium channel blockers like amlodipine and beta-blockers like metoprolol are usually continued, and beta-blockers should not be stopped suddenly. Check your specific list with your pharmacist.
Can I take extra doses to make up for the ones I skipped?
No. Do not double up to replace skipped sick-day doses. Once you are well, simply restart your normal schedule. Taking extra can drop your blood pressure too low, especially if you are still recovering.
This article provides general information about medication management and is not a substitute for professional medical advice. Always consult your doctor or pharmacist before making changes to your medication schedule.
