Wait... vegetarian wine? But isn't all wine made of grapes? It indeed is, but it can go through processing steps that involve animal products. In winemaking, the troublesome ingredients come into play during the finishing, also called fining or clarifying phase.
The ingredients that may be used and will make the drink not suitable for vegetarians are for example isinglass (which is made from fish bladders), gelatin (which comes from cow bones) and animal albumin (which sometimes consists of dried blood powder). Though none of these fining agents stay in the finished product, most vegetarians and vegans will try their best to drink beverages where no animal products have been used during the making process.
Luckily for them and me, there are vegetarian wine options available. Not all wines go through fining at all, and even if they do, there are vegetarian finishing options which are used, like bentonite clay.
It can be frustrating for vegetarians and vegans to know that there is no obligation on the part of winemakers to declare the use of animal by-products in the winemaking process. In fact, the only real way of knowing if a wine is vegetarian is to look at what is written on the label of the bottle, or the specifications on the website you are buying the bottle from. If it says vegetarian or vegan on the site or the label, it probably is.
If there are no such markings on the label or the website, you can be pretty sure the wine is non-vegetarian - isinglass is still the number one fining agent used in winemaking.
The only exceptions are wines which are labeled as unfiltered. This is in fact not a very rare label, because some wine connoisseurs prefer wine to be unfiltered because of the special character of these wines.
Most good shops for buying wine on line will write in the product description if the wine is vegetarian or vegan. Not all bigger shops on line are interested in offering vegetarian wines, though. It can be beneficial to look in smaller on line wine stores instead.
Especially shops specialized in organic wines have been known to have a wide range of vegetarian and vegan wines in their selection, and these are usually very well labeled, too. You could try your local wine shop to see what they have, but you'll be likely to find the best selection of vegetarian wines on line.