If your kit uses a blood collection card, the card must dry completely before you seal it in its bag. Sealing a card while the blood is still wet traps moisture inside the packaging, which damages the sample — and is one of the most common reasons the lab rejects a blood card. A rejected card means starting over with a new collection.
What goes wrong if a card is sealed wet
When a card is packaged before it is fully dry, the trapped moisture breaks down the blood cells — a process called hemolysis. A hemolyzed sample cannot be analyzed accurately, so the lab will reject it and you will need to collect a new sample.
Hemolysis can also occur if you pause too long between drops while you collect. Work steadily so each drop goes onto the card without long gaps, then let the finished card dry fully before you package it.
How long to dry your card
Drying time depends on your specific card type, so follow the time printed in your kit's instructions. Common drying windows include:
About 30 minutes for some card types.
About 45 minutes to 1 hour for others.
Up to 3–4 hours for certain dried blood spot card types.
A fully dried spot looks dark brown and matte — not wet, shiny, or tacky.
How to dry your card correctly
Lay the card flat on a clean, dry surface immediately after collection.
Keep it away from direct heat, direct sunlight, and humidity. Do not use a hair dryer, oven, or any other heat source.
Do not stack cards on top of each other or place them in the bag until they are completely dry.
Once the card is fully dry, seal it in its biohazard bag. Add the desiccant packet if your kit includes one.
Note: If you cannot mail the sample right away, store the dried, sealed card in a cool, dry place and ship as soon as possible. Avoid mailing on a Friday or the day before a holiday so the sample does not sit in transit over a weekend.
Need more help?
If you are not sure whether your card is fully dry, contact our support team through chat. There is no cost for a replacement collection kit when a new sample collection is needed for the lab to complete your analysis.