ACE inhibitors lower blood pressure by blocking a key step in your body’s blood pressure regulation system. They’re one of four first-line drug classes recommended for treating high blood pressure, and they also protect the heart and kidneys in several other conditions. Lisinopril, enalapril, and ramipril are among the most commonly prescribed.
How ACE Inhibitors Work
Your body has a built-in system for raising blood pressure called the renin-angiotensin system. Here’s the short version: your kidneys release an enzyme called renin, which triggers a chain reaction that eventually produces a powerful blood vessel constrictor called angiotensin II. That substance tightens your blood vessels and signals your body to retain sodium and water, both of which raise blood pressure.
ACE inhibitors block the enzyme (angiotensin-converting enzyme) responsible for creating angiotensin II. With less angiotensin II circulating, your blood vessels relax and widen, your body holds onto less salt and water, and your blood pressure drops. The effect also reduces the production of aldosterone, a hormone that further promotes fluid retention. Beyond the blood pressure drop, lowering angiotensin II has deeper benefits: it reduces the production of inflammatory signals, tissue-damaging free radicals, and compounds that promote scarring in blood vessels, the heart, and the kidneys.
One thing worth knowing is that a single daily dose only suppresses angiotensin II levels for a few hours after you take it. Over time, your body can partially work around the blockade, which is why consistent daily use matters and why your provider may adjust your dose or add a second medication.
Conditions They Treat
High blood pressure is the most common reason people take ACE inhibitors, but the list of uses is broader than many people realize:
- High blood pressure: ACE inhibitors are one of the four drug classes with the strongest trial evidence for lowering blood pressure and preventing heart disease and stroke.
- Heart failure: They reduce the workload on a weakened heart by relaxing blood vessels and lowering fluid volume.
- After a heart attack: They help the heart recover and reduce the risk of further damage.
- Stroke and heart attack prevention: In people at high risk for either event, ACE inhibitors offer protective benefits even when blood pressure isn’t dramatically elevated.
- Kidney disease: They slow the progression of kidney damage, particularly in people with diabetes. They’re also used for conditions like nephrotic syndrome, excess protein in the urine, and problems with the kidney’s filtration system.
Why They’re Especially Important for Kidneys
ACE inhibitors do something for the kidneys that most blood pressure drugs don’t. Inside each kidney, tiny filtering units called glomeruli operate under their own internal pressure. Angiotensin II raises that internal pressure, which over time damages the filters and allows protein to leak into the urine. ACE inhibitors lower the pressure inside those filters specifically, not just your overall blood pressure.
In clinical trials, ACE inhibitors reduce protein leakage in the urine by roughly 35% to 40%, which is significantly more than other blood pressure medications even after accounting for the blood pressure drop itself. That protein leakage isn’t just a lab number: filtered proteins trigger inflammation inside the kidney, accelerating damage. By plugging that leak, ACE inhibitors slow the cycle of kidney deterioration.
Current guidelines from the American Heart Association and American College of Cardiology recommend ACE inhibitors (or the closely related ARBs) as the preferred first-line treatment for people who have both high blood pressure and chronic kidney disease with significant protein in the urine. For people with diabetes and kidney involvement, ACE inhibitors are specifically recommended to delay progression of diabetic kidney disease.
Common ACE Inhibitors
There are about ten ACE inhibitors available. The most widely prescribed include lisinopril, enalapril, ramipril, benazepril, and captopril. Others include fosinopril, moexipril, perindopril, quinapril, and trandolapril. They all work through the same mechanism, but they differ in how long they last, how they’re processed by the body, and which specific conditions they’ve been studied for. Your provider picks one based on your situation, other medications, and how your body responds.
Side Effects to Expect
The most distinctive side effect is a persistent dry cough, which occurs because blocking ACE causes a buildup of a substance called bradykinin in the lungs. It’s not dangerous, but it’s annoying enough that some people switch to an ARB, which works on the same system without affecting bradykinin. The cough typically goes away within a week or two of stopping the medication.
Dizziness, especially when standing up quickly, can happen because the medication lowers blood pressure. This is more common in the first few days or after a dose increase. Headache and fatigue are also reported early on.
A less common but more serious concern is angioedema, a rapid swelling of the face, lips, tongue, or throat. This is rare but requires immediate medical attention because it can obstruct breathing.
Potassium and Diet
ACE inhibitors cause your kidneys to retain potassium instead of excreting it, which means your blood potassium levels can rise. For most people eating a normal diet, this isn’t a problem. But it becomes a real concern if you’re also consuming high-potassium foods in large amounts or, more critically, using potassium-based salt substitutes. Products marketed as “lite salt” or low-sodium alternatives often replace sodium chloride with potassium chloride, and combining these with an ACE inhibitor can push potassium to dangerous levels.
Check food labels for “KCl,” “K+,” or “potassium” in the ingredients. Chocolate, molasses, and certain salt substitutes are particularly high. Your provider will likely monitor your potassium with periodic blood tests, especially early on or if you have kidney disease.
Who Should Not Take Them
ACE inhibitors are not safe during pregnancy. Use during the second and third trimesters is associated with a pattern of fetal harm that includes impaired kidney development, skull abnormalities, and restricted growth. The FDA warned against their use in pregnant women, and the risk extends to anyone who could become pregnant without reliable contraception.
People who have had angioedema from an ACE inhibitor should not take one again. ACE inhibitors also should not be combined with ARBs, since both block the same system at different points, and the combination increases the risk of side effects like dangerously high potassium and kidney problems without providing a meaningful additional benefit for most people.