Hi All,

You all probably already know that guar gum interferes with
metformin, but in case you didn't:

http://www.ncbi.nlm.nih.gov/pubmed/2722133

Horm Metab Res. 1989 Feb;21(2):81-3.
The influence of Guar gum on absorption of metformin from
the gut in healthy volunteers.

Gin H, Orgerie MB, Aubertin J.

Clinique Médicale et des maladies infectieuses, Hôpital Pellegrin,
Bordeaux, France.

Abstract

Dietary fibre and biproducts of some vegetable extracts (Guar etc.)
are advocated to reduce postprandial hyperglycaemia but there is
some evidence that these may disturb the absorption kinetics of
orally administered drugs. The effect of Guar gum on the digestive
absorption of metformin was tested in 6 healthy subjects given
1700 mg of metformin with a standardised meal. Metformin blood
levels showed that when given together with Guar there was a
reduction in the absorption rate over the first 6 hours. These
findings suggest that combination therapy may diminish the
anti-hyperglycaemic action of metformin.