Which form of Metformin is available as a solution?

Riomet is the correct choice because it is specifically formulated as an oral solution containing metformin. This liquid form can be particularly beneficial for patients who have difficulty swallowing tablets or for those who prefer a liquid medication.

In contrast, Fortamet and Glucophage XR are both extended-release formulations of metformin that come in tablet form and are not available as solutions. Regular Metformin is also available primarily in tablet form; while it can occasionally be compounded into a liquid by pharmacies, it is not marketed as a liquid solution like Riomet. This distinction is important in understanding the available formulations of metformin and their appropriate usages for patients.