Should i take Bank Islam personal loan which offers 5.1% per annum to clear my 18% credit card debt?

No, not if you are a muslim. According to the Shari’a principles, a dedicated Muslim must not deal with those banks that directly or indirectly charge interest (riba) from or pay interest to their customers. In principle, a Muslim that does not accept riba but banks with a financial institution that deals with riba, is in the same position as that Muslim who directly accepts interest. Hence, a devout Muslim must not deal with any bank that offers conventional banking products. To demean this rule, global banks have gone as far as employing the so called Shariá Boards that constitute of groups of 6 or more Muslim sheiks (O’lama: Islamic banking experts) who placed hundreds of fatwa’s (religious interpretations) to make dealings with them legitimate according to Islamic values. Although they were not so convincing, yet they managed to built their Islamic banking business. Their success is solely attributed to the failure of genuine Islamic Banks to offer the Muslims services at standards adequate to secure their rights and protect their interest, especially with regard to trade finance and investment transactions.

if you save by doing so & if you are satisfied of their dael, you may proceed ,