Replied by Robert (Martinez, Ca) on 06/20/2016
'General' expiration is 1-year unopened & 9-months after opening. Dates vary according to some mfgr's such as Crow's who states 5-10yr life. One source says 30yrs. Tablets last longer than liquid & per 'authorities' here, (FDA, NRC, etc.), indefinitely if stored properly. Manufacturers are required to post a expiration date which is not 'actual' but merely meeting the requirement to post. Even beer has a exp. date! It's a reference but is important on compound meds where the chems lose strength or 'morph' into unknown potentially toxic substances. "30 days" for your Lugols is questionable based on net searches.
