You can consume item using the following code
mHelper.consumeAsync(inventory.getPurchase("item_id"),
mConsumeFinishedListener); and check consumption succeed or not here :
IabHelper.OnConsumeFinishedListener mConsumeFinishedListener =
new IabHelper.OnConsumeFinishedListener() {
public void onConsumeFinished(Purchase purchase, IabResult result) {
if (result.isSuccess()) {
// provision the in-app purchase to the user
// you can mark here that item has been consumed so you can purchase it again
}
else {
// handle error
}
}
};