6. Inventories

Inventories consist of the following (in thousands):

Work-in-process and finished goods as of December 31, 2022 and 2021 include conversion costs and exclude the cost of insulin. All insulin inventory on hand was written off and the projected loss on the purchase commitment contract to purchase future insulin was accrued as of the end of 2016. Raw materials inventory included $0.8 million of pre-launch inventory as of December 31, 2022 and 2021, which consisted of FDKP received in November 2019 that will be used to manufacture Afrezza under an enhanced manufacturing process for FDKP. The Company expects to receive FDA approval of the new source of FDKP in 2024.

The Company analyzed its inventory levels to identify inventory that may expire or has a cost basis in excess of its estimated realizable value. The Company also performed an assessment of projected sales and evaluated the lower of cost or net realizable value and the potential excess inventory on hand at December 31, 2022 and 2021. Inventory that was forecasted to become obsolete due to expiration as well as inventory that does not meet acceptable standards is recorded in costs of goods sold in the accompanying consolidated statements of operations. There was an inventory write-off of $2.2 million as a result of this assessment for the year ended December 31, 2022. For the year ended December 31, 2021, there was an inventory write-off of $1.9 million as a result of this assessment, including $0.7 million related to the start of an agreement with a retail pharmacy. There was an inventory write-off of $0.5 million for the year ended December 31, 2020.