The present invention provides methods for determining a ratio of an amount of a glycated form of a protein to a total amount of the protein in a sample containing the glycated protein, the glycosylated protein, or the glycoprotein. The method incorporates lateral flow test strip or vertical flow test strip devices having negatively charged carboxyl or carboxylate groups and hydroxyboryl groups immobilized and interspersed on a solid support matrix. The solid support matrix may include derivatives of cellulose (e.g., carboxy cellulose) derivatized with carboxylic acid (e.g., carboxylate, carboxyl) groups and hydroxyboryl compounds including phenylboronic acid (e.g., phenylborate), aminophenylboronic acid, boric acid (e.g., borate), or other boronic acid (e.g., boronate) compounds. The present invention is usefi.il for monitoring glycation or glycosylation of hemoglobin or albumin for monitoring glycemic control (e.g., glycemia in diabetes).