Are your feet swollen? Your ankles puffy? When it’s normal…when it’s not…and what to do about it…

What happens: Your body usually maintains a precise fluid balance. It holds on to fluids when you need them, and it excretes fluids when you have too much. Anything that disrupts this balance can cause fluids to accumulate.

The fluids usually go downhill. Fluid in the feet or lower legs has to push its way upward, against gravity. If your veins aren’t as robust as they should be or if you’re sedentary and your leg muscles aren’t flexing against the veins, the fluid tends to pool and cause swelling. This is called peripheral edema.

Self-test: Press a finger on your foot/ankle. If the area stays indented for more than a few seconds, you probably have some degree of peripheral edema.

A dangerous sign: Mild swelling that comes and goes usually is harmless. But see your doctor if you have swelling much of the time, especially if you also have shortness of breath or high blood pressure. Swelling can be caused by heart or kidney damage, liver problems or damage to the veins.

Red flag: Painful swelling that occurs in one leg, foot or ankle. It’s a classic sign of a blood clot. A clot that forms in one of the deep veins in the legs, a condition known as deep-vein thrombosis, is potentially deadly. Get to an emergency room immediately.

Common causes of swelling…

Too much salt. Your body has a natural defense against excessive salt-it retains fluids to dilute it. People who are sensitive to salt or whose kidneys are unable to excrete it efficiently may notice foot or leg swelling after eating a single high-salt meal.

Medications. Swelling is a side effect of many drugs. These include the hormones in oral contraceptives, some antidepressants and blood pressure medications and even the common painkiller naproxen (brand names Aleve and Naprosyn, among others).

Overweight. Pressure from extra weight can make it harder for blood to move uphill. Also, people who are overweight tend to develop other health problems, including diabetes and heart disease, that interfere with circulation.

Prolonged standing or sitting. Fluid tends to pool.

To reduce swelling: Lose weight, limit salt and…

Keep your feet moving, particularly during plane flights or car trips. Flexing the feet and ankles causes muscles to press against veins, which prevents blood from pooling. And don’t cross your legs. It puts pressure on the veins, making it harder for fluids to circulate.

Raise your legs. Once or twice a day, lie down and prop your legs against a wall or on a chair or a stack of pillows. It’s makes it easier for blood to exit the legs and return to the heart. For sleeping, raise the bottom of your bed by putting each bottom bed leg on a brick or book.

Wear compression stockings. The over-the-counter stockings sold at pharmacies exert enough pressure to “firm up” the veins and improve blood flow. I recommend them for waitresses, police officers and other people who are on their feet all day.

Drink more water. It flushes excess sodium from the body.

For more information about painful feet, see our Facebook chat with Dr. Youner, “Why Do My Feet Hurt?