There are now several (positive) studies on this nutrient-combination. Here's the most recent one ...
In a randomized, double-blind, placebo-controlled study involving 447 subjects with poorly controlled type 2 diabetes (HbA(1c) = 7.0% or greater), supplementation with chromium picolinate (600 mcg Cr(+3) per day) with biotin (2 mg/d) for a period of 90 days, in combination with oral anti-diabetic agents, was found to significantly reduce HbA(1c) (reduction of 0.54%), and fasting glucose levels (reduction of 9.8 mg/dL), as compared to subjects who received a matching placebo.
In subjects with baseline HbA(1c) of 10% or higher, even more dramatic improvements were found to be associated with chromium picolinate and biotin treatment - HbA(1c) reduced by 1.76% and fasting glucose reduced by 35.8 mg/dL. The treatment with chromium and biotin was well tolerated with no significant adverse effects.
The authors conclude, "These results suggest that the chromium picolinate/biotin combination, administered as an adjuvant to current prescription anti-diabetic medication, can improve glycaemic control in overweight to obese individuals with type 2 diabetes; especially those patients with poor glycaemic control on oral therapy."
The commercial name of this product is Diachrome
. Here's more information about it.