Pedal edema is swelling in the feet and ankles caused by excess fluid trapped in the tissues. The fluid builds up in the spaces between cells, making your feet look puffy, feel tight, and sometimes leaving a visible dent when you press on the skin. It can affect one foot or both, and the pattern often points to different underlying causes.
How Fluid Builds Up in Your Feet
Your body constantly moves fluid between your blood vessels and the surrounding tissues. A balance of pressures inside and outside the vessel walls keeps this exchange steady. When something disrupts that balance, fluid leaks out of blood vessels faster than your lymphatic system can drain it away, and it pools in the lowest point gravity pulls it: your feet and ankles.
Several forces can tip this balance. Increased pressure inside blood vessels pushes more fluid out. Low protein levels in the blood reduce the pull that keeps fluid inside vessels. Damaged vessel walls become leakier. And a sluggish lymphatic system fails to clear the excess. Even standing still for a long time raises the pressure in your foot capillaries by more than 50 mmHg compared to lying down, which is why your feet swell on long flights or after hours on your feet, even when nothing is medically wrong.
Swelling in One Foot vs. Both
Whether the swelling is in one leg or both is one of the most important clues to its cause. Symmetric swelling in both feet generally points to a systemic problem: heart failure, kidney disease, liver disease, or a medication side effect. Asymmetric or one-sided swelling is more likely a local problem, such as a blood clot, damaged veins, or a lymphatic blockage.
The two most common causes of swelling in a single leg are deep vein thrombosis (DVT) and lymphedema. In DVT, a blood clot blocks a vein, and the swelling may stay below the knee if the clot is in a lower leg vein or extend up to the groin if it is higher. DVT is a medical emergency because a clot can break loose and travel to the lungs. Warning signs that this has happened include sudden shortness of breath, sharp chest pain that worsens when you breathe in, and fainting.
Common Systemic Causes
Heart Failure
When the heart can’t pump blood efficiently, blood backs up in the veins and pressure rises in the capillaries, forcing fluid into the tissues. At the same time, reduced blood flow to the kidneys triggers hormonal systems that tell your body to hold onto sodium and water, making the problem worse. This creates a cycle: the heart struggles, the kidneys retain fluid, blood volume rises, and more fluid leaks into the feet. In heart failure, pedal edema typically worsens over the course of the day and improves overnight when you lie flat.
Kidney Disease
Healthy kidneys filter excess sodium and water out of the blood. In advanced kidney disease, that filtering capacity drops and extracellular fluid volume can increase by up to 30%, leading to visible swelling. Kidney disease can also cause the body to lose protein in the urine, which reduces the blood’s ability to hold onto fluid inside vessels.
Liver Disease
The liver produces albumin, the main protein responsible for keeping fluid in the bloodstream. When liver function declines, albumin levels fall and fluid shifts into the tissues. Cirrhosis also raises pressure in the veins draining the abdomen, contributing to swelling in the legs and fluid accumulation in the belly.
Vein Problems and Chronic Swelling
Chronic venous insufficiency is one of the most common causes of persistent pedal edema in otherwise healthy adults. The valves inside leg veins are supposed to keep blood moving upward toward the heart. When those valves weaken or fail, blood pools in the lower legs, raising pressure in the small vessels and pushing fluid out into the tissue.
Over time, this ongoing pressure damages the skin. You may notice brownish discoloration around the ankles, dry or flaky patches, or thickened, hardened skin on the lower calves. These changes develop gradually and are a sign that the venous congestion has been present for a while. Previous blood clots in the deep veins are a common trigger, but vein valve failure can also develop without a clear cause, especially with age, obesity, or prolonged standing.
Medications That Cause Foot Swelling
Several widely prescribed medications cause pedal edema as a side effect. Calcium channel blockers used for high blood pressure are among the most common culprits. Drugs like amlodipine, nifedipine, and felodipine dilate arteries more than veins, which raises capillary pressure and pushes fluid into the tissues. This type of edema is dose-dependent, meaning it gets worse at higher doses.
Other medications linked to foot swelling include:
- NSAIDs (ibuprofen, naproxen), which promote sodium retention
- Steroid hormones, including corticosteroids and estrogen-based therapies
- Diabetes medications in the thiazolidinedione class
- Blood pressure drugs like hydralazine and minoxidil
An important distinction: edema from calcium channel blockers is not caused by excess fluid volume in the body, so standard diuretics often don’t resolve it well. Edema from drugs like hydralazine or minoxidil, on the other hand, involves true fluid retention and typically responds to diuretics.
Pedal Edema During Pregnancy
Some swelling in the feet is normal during pregnancy, especially in the third trimester, as the growing uterus compresses veins returning blood from the legs. This kind of swelling tends to develop gradually, worsen in the heat or after standing, and resolve with rest.
Sudden swelling is different. A rapid onset of edema, particularly in the face and hands along with the feet, can be a sign of preeclampsia, a serious condition involving high blood pressure that develops after 20 weeks of pregnancy. Sudden weight gain over a few days is another red flag. Preeclampsia requires prompt medical evaluation because it can affect both mother and baby.
The Pitting Test
Pressing a finger firmly into swollen skin for several seconds and then releasing it is the simplest way to assess pedal edema. If your finger leaves a dent that takes time to fill back in, that’s called pitting edema. Doctors grade pitting on a scale from 1+ to 4+ based on how deep the dent is and how long it takes to rebound. A shallow dent that disappears quickly is mild (1+), while a deep dent that persists for 30 seconds or more is severe (4+).
Not all swelling pits. Lymphedema, for example, often produces a firmer type of swelling that doesn’t indent as easily, especially in later stages when the tissue becomes fibrotic. The presence or absence of pitting, along with whether one or both legs are affected, helps narrow down the cause.
How Pedal Edema Is Managed
Treatment depends entirely on the cause. When a systemic condition like heart failure or kidney disease is driving the swelling, the primary goal is treating that condition. Loop diuretics are the most potent option for removing excess fluid. They work by blocking sodium reabsorption in the kidneys, which increases urine output and pulls fluid out of swollen tissues. If one type of diuretic isn’t enough, doctors sometimes combine two that work on different parts of the kidney to enhance the effect. Limiting salt and fluid intake helps prevent the body from re-accumulating fluid between doses.
For medication-induced edema, switching to a different drug or lowering the dose is often the most effective solution. If you notice your feet swelling after starting a new prescription, that connection is worth bringing up with your prescriber.
Practical Steps That Help
Regardless of the underlying cause, a few strategies consistently reduce swelling. Elevating your legs above heart level for 20 minutes, three times a day, has been shown to produce a measurable reduction in leg edema. Compression stockings apply gentle, steady pressure that helps push fluid back into the veins and lymphatic vessels. Studies in diabetic patients found that even mild compression socks significantly reduced ankle and calf swelling without cutting off circulation. Walking and calf exercises activate the muscle pump in your lower legs, which squeezes blood upward through the veins and reduces pooling.
Reducing salt intake matters more than most people expect. Sodium holds water in your bloodstream and tissues, so a high-salt diet directly works against any other effort to reduce swelling. This is especially important if you’re taking diuretics, since your body tends to compensate by retaining extra sodium between doses.