Is it harmful or dangerous to take expired medicine?

Loss of potency: For the most part, it is not dangerous as expired medications begin to loose potency and effectiveness (and thus one may be harmed by taking a sub-optimal dose.) the exception is the tetracycline family of medications where taking expired tetracycline can cause liver damage.

Generally ok: With rare exceptions (tetracycline, nitoglycerine and Insulin for example) most medications are generally safe upto 15 years after the expiration date. This was demonstrated by a study done by government on medications stored by the military. The date is required by the fda to certify that a medication is fully potent.

Depends: Tetracyclines can be harmful if expired. Most medications just lose potency but will not harm you. Most medications remain just as potent for at least 6 months beyond the stated expiration date.

Maybe: The expire date is the last date the manufacturer can guarantee effectiveness. Sure a lot of medicine remains effective beyond that, but not guaranteed. A lot of meds are very shelf stable provided they've been kept in good condition. But your steamy bathroom medicine cabinet is not the safest shelf in the world. A few meds degrade into something more harmful but mostly they just stop working.

Maybe: Pills do not turn into pumpkins at midnight on their expiration date. There is probably some room for error when an expiration date is placed on a label. But why be so cheap on something as important as your health? If it is a prescription, you probably ought to go get a refill (to confirm the medication is still indicated!) and if otc, just splurge on a fresh bottle.

Can be: Depends a bit on the med, but most become less effective, which could be dangerous and certainly makes using them a problem for whatever you're treating. Essentially no drugs become dangerous in the sense of being poisonous. Typically it's not like food expiry, for drugs the date is certainly "use by", not "sell by".

Possibly: Most meds are still safe a couple months past the expiration date. A few, however, may not be: liquid meds may evaporate, leaving a more concentrated dose; expired tetracyclines can cause fanconi syndrome, a disease of the kidneys, & liver damage.

Yes, it can be: Expired medications may no longer have the same effects on the body and may interact with other medications your health care provider has prescribed. People with younger children in the household should be aware of the risk of accidental ingestion of medications, especially expired medications. You should dispose of expired or uncessarily medications.