Katakana has many functions. To check whether you are dealing with a Japanese word (where katakana has been used for emphasis, or in a scientific context, or...) or a word that is a loanword from a foreign (often Western) language, it suffices to check an ordinary monolingual dictionary, for example 大辞泉 via https://kotobank.jp/.
You don't need to be able to read the whole Japanese definition as the etymology of loanwords is listed at the beginning and in the Latin alphabet so you can't miss it. For example,
If you are dealing with a native Japanese word, it is usually listed with ひらがな or 漢字 (probably with exceptions). For example, ダメ would be listed as
and the katakana here are for emphasis/slangyness,
There are also slang words like ググる (from グーグル Google), some of which have become standard (like サボる). For more on this take a look at Are there words which consist of katakana and hiragana letters together?