In our Houston and Dallas area vein clinics, we see many people with peripheral edema—which is swelling of your feet and ankles due to fluid build-up–who ask why do my feet swell? Most of the patients we see for edema have fluid trapped in the soft tissues of their legs, and this buildup is due to malfunctioning valves in their veins.
But where does that fluid come from? It seeps out of your small blood vessels and collects in nearby tissue. Then, your sodium (salt) and water levels increase.
Next, your kidneys respond by circulating more blood around your body; this only starts a cycle that can lead to more leaking fluid and increased swelling. Now, when things are working properly, your lymphatic system should get rid of that excess fluid, but when it isn’t up to the challenge, you’ll notice fluid build up.
If you have swollen legs or feet, the edema could be a symptom of vein disease: when the valves in your leg veins weaken or fail, the blood can no longer be pumped properly out of your legs. This causes blood and fluid to stick around and, as the fluid builds up, your leg may begin to swell—hence, edema.
What About Lymphedema? 
Related to edema is lymphedema, a form of chronic edema that develops when your body’s lymphatic system isn’t functioning properly. It’s different than the edema tied to vein-disease. But it’s important to understand that vein disease is progress, and so you may end up with both vein disease and a lymphatic disorder. As with swelling in the lower legs, lymphedema requires the attention of a healthcare professional as soon as possible. Otherwise, lymphedema can lead to serious complications, including leg amputation, as was recently the case for Bachelorette Season 15 contestant Cam Ayala.
Now, primary edema is the main cause of swelling in a vein clinic, but other factors may leave you with edema as well. However, if your legs are swollen and you don’t know why, you need to take action. First, rule out the causes we’re about to review. And if none of those make sense, come and see us for a diagnostic vein ultrasound. Because, even now, even in the time of COVID-19, it’s just not safe to ignore your vein health.
9 Reasons Your Feet Swell That Aren’t Vein Disease
Already ruled out these potential causes? It’s time to see your vein doc. Otherwise, check and see if:
Your Feet Swell After a Long Flight or Drive
As it turns out, you can develop vein-disease like symptoms from sitting too long. That’s because your veins get less effective at pushing blood up to your heart, allowing it to pool and making your feet swell up. Why? The problem is sitting: it limits your muscle contractions, making it harder for blood to move. But the position also pushes on your veins, which further reduces the blood flow…and, voila, edema!
Your Feet Swell Because you’re Sedentary
When you don’t exercise, your circulatory system can become compromised. Especially if you’re also carrying extra weight around. Bring those two factors together, and swollen feet and legs may be the result.
You’ve Been Slamming Salty Snacks
This cause of edema actually has nothing to do with your blood flow. Plain and simple—salt makes you retain water. And if that water sticks around your feet and legs, they get swollen!
You’re Hurt
When you’re dealing with injuries in your feet or ankles—whether it’s an acute issue like a sprain or fracture, or an overuse injury like shin splints—swelling may ensue. And while this may look like edema, the symptom is completely unrelated, and will only disappear when your underlying injury is treated.
You’re Taking A New Medication
Some medications can cause fluid retention or swelling in your legs, ankles or feet. So if your edema appears shortly after starting a new drug—especially for conditions like high blood pressure—check in with your prescribing doctor to see if the two are connected.
You’re Developing a DVT
In the beginning stages of deep vein thrombosis (DVT), your legs are sore and often swollen. Remember, a DVT is a blood clot in your deep leg veins, and it’s a medical emergency. That’s because if your clot breaks free and travels to your lungs (pulmonary embolism), your condition becomes life-threatening. Therefore, if you have any DVT risk factors (long air travel, pregnancy, smoking, taking oral birth control or medical history of clotting) and your feet swell, see your vein specialist immediately.
You’ve Got Arthritis
Your joints are inflamed when you have arthritis. And, sometimes, this inflammation causes swelling, especially around your ankles or big toe (gout.) If you’ve noticed localized swelling and feel stiff or achy, you should consult with a joint specialist as soon as possible.
Heart or Kidney Problems are Brewing
As we mentioned earlier, your kidney play a role in regulating fluid buildup in your body. When they aren’t functioning properly, they are unable to remove excess fluid, and you may develop edema. Similarly, when your heart isn’t working effectively, it can’t sufficiently pump blood around your body, allowing pressure to build up in your blood vessels. This can trigger the type of leaking fluid we initially discussed. And it’s why swollen feet and ankles are a common symptom of congestive heart failure, and hypertensive heart disease.
Liver Disease
When your liver is diseased, your hormone levels are impacted, as are the chemicals in your body which regulate fluids. Therefore, you may retain fluid and notice swollen feet and ankles with liver disease.
Now we’ve thoroughly explored non-vascular edema triggers. So, we have to remind you: lots of times, this symptom is an indication of problems in your veins. And that means that, if you’ve got swollen legs and you’re not sure why, go and see an experienced vein specialist to get a diagnosis.
Sources: Foot Pain Explored