I bought my SN from a reputable source about 2 years ago.
How important is it to test it?
I'm really struggling with getting my blood.
If you didn't open it yet, the SN should still be good. The shelf life for unopened SN is at least 3 years. On the website of a reputable seller of SN it says:
Under proper storage conditions, the shelf life for dry sodium nitrite is at least 3 years. While sodium nitrite may cake, clump and harden within 6 months of the manufacture date, the chemical assay will remain within manufacturing specifications for at least 3 years. The table below summarizes the shelf life across ………… dry sodium nitrite product line.
Dry Sodium Nitrite Shelf Life Guidance
Minimum Shelf Life. 3 years
Free-Flowing Food Grade 3 years Free-Flowing Technical Grade 3 years
High Purity Granular. 3 years
High Purity Special Granular. 3 years
High Purity Flake. 3 years