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Spider veins are thin red or blue threads, under 1 mm across, flat against the skin. Varicose veins are 3 mm or wider, raised, and often ropey. That size difference is the whole distinction, and it is the one doctors use. Everything else, from cause to treatment to whether insurance pays, follows from it.
The classification system used worldwide for vein disease, called CEAP, draws the line at exactly that width. Varicose veins are “distinguished from reticular veins by a diameter of 3 mm or more,” per the CEAP reference. Spider veins, which the system calls telangiectasies, and the slightly larger blue reticular veins sit below that line in a single class of their own.
The three sizes, side by side
| Spider veins | Reticular veins | Varicose veins | |
|---|---|---|---|
| Width | Under 1 mm | 1 to 3 mm | 3 mm or more |
| Look | Fine red or purple threads, often in a web | Flat blue lines, usually behind the knee or on the thigh | Raised, twisting, blue or skin-colored cords |
| Feel | Flat | Flat | Bulge under the finger |
| Usual cause | Sun, hormones, family history, standing | The same, sometimes fed by a failing deeper vein | A failed valve in the saphenous vein |
| Symptoms | Usually none | Usually none | Aching, heaviness, swelling, itching |
| CEAP class | C1 | C1 | C2 |
The two flat types share a class because they behave the same way. The raised type gets its own class because it is a different disease.
Why varicose veins are the one that matters medically
A varicose vein is the visible end of a problem that starts higher up. The saphenous vein, which runs from the ankle to the groin under the skin, has one-way valves. When a valve fails, blood falls back down the leg instead of returning to the heart, and the pressure that builds is what balloons the surface veins. That pressure is also what causes the aching, the evening swelling, and eventually the skin damage. Our page on varicose veins covers the whole progression.
Spider veins do not usually come from that mechanism. Most are a local skin-level change from sun, hormones, pregnancy or simply family history. They do not carry pressure and they do not damage anything. The NHS lists female sex, age, weight, pregnancy, prolonged standing and family history as the risk factors for varicose veins, and most of the same list applies to spider veins, which is part of why people assume they are the same thing.
When spider veins are a clue, not just a cosmetic issue
A cluster of spider veins around the inner ankle, sometimes called a corona, can mean a refluxing vein is feeding them from below. So can spider veins that keep coming back after treatment. In those cases the spider veins are the smoke, and the ultrasound finds the fire. This is the main reason we scan before treating spider veins in someone who also has aching or swelling: treating the surface without fixing the feeder means the spider veins return within months.
How each one is treated
Spider veins are treated with sclerotherapy, a series of injections of a solution that irritates the vein lining so the vein closes and fades. The treated veins look worse for a week before they fade, which we explain in sclerotherapy after 1 week. It is quick, needs no anesthetic, and most people need two or three sessions spaced a few weeks apart. It is considered cosmetic, so it is paid for directly.
Varicose veins are treated by closing the failing vein that feeds them. That is done in our office with Varithena, an ultrasound-guided foam, or laser ablation, a thin fiber that seals the vein from inside. Once the pressure is gone, the surface veins shrink, and any that remain can be removed through tiny nicks or treated with sclerotherapy. Because this is treating a medical condition, insurance usually covers it once reflux is documented on ultrasound.
The honest part
Sclerotherapy fades spider veins. It does not stop new ones forming, and people who are prone to them will get more over the years. Expect maintenance sessions rather than a one-time fix. And if the ultrasound finds reflux under a patch of spider veins, we will tell you the spider veins are the smaller problem, even when they are the one you came in about.
Varicose vein treatment closes the vein that is treated. It cannot stop another valve failing years later, which happens in a minority of people. Follow-up ultrasound is how that gets caught early.
Which do you have?
If the veins are flat and you can not feel them, they are spider or reticular veins. If they stand up from the skin and you can trace them with a finger, they are varicose. If you have both, or the flat ones come with aching and swelling, book a consultation and ultrasound and we will map what is feeding what before recommending anything.
Questions people also ask
Can spider veins turn into varicose veins?
No. They are different vessels. Spider veins stay small. What can happen is that a failing deeper vein causes both at once, so someone who has spider veins now develops varicose veins later from the same cause.
Does insurance cover spider vein treatment?
Almost never, because it is cosmetic. Both of the Medicare coverage policies that apply in the Midwest say spider vein treatment is not covered unless the vein has bled. Varicose vein treatment with documented reflux and symptoms usually is covered.
