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How much blood is enough?

How to tell if you've collected enough blood, and how to avoid a Quantity Not Sufficient result.

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Written by Riley Burcin

You have collected enough blood when your tube reaches its fill line or every circle on your collection card is fully saturated. Not collecting enough blood is the most common reason a blood sample is rejected by the lab — this is called a "Quantity Not Sufficient" (QNS) result. A few minutes of preparation before you start prevents this.

Know your target

The right amount of blood depends on which type of collection container your kit includes. The table below summarizes the two main types.

Kit type

Target

Tube kit

Fill the tube to the fill line marked on the side

Card kit

Fill every printed circle so the blood saturates each one from edge to edge (roughly 4–6 large drops per circle for most cards)

Always follow the markings on your specific kit — these are the authoritative targets for your test.

Important: For card kits, use one large drop per circle and let it spread naturally to fill the circle. Do not layer many small drops or overfill. Supersaturating the card — putting too much blood on it — can also cause the lab to reject the sample.

How to get enough blood

Most Quantity Not Sufficient problems trace back to cold hands or dehydration. To keep blood flowing during collection:

  1. Drink 8–16 oz of water in the 1–2 hours before you collect.

  2. Warm your hands under warm water or hold a warm (not hot) cloth against your fingertip for at least 1–2 minutes.

  3. Let your hand hang below waist level so blood pools in your fingertips.

  4. Prick the side of your fingertip, not the soft center pad.

  5. Gently squeeze from the base of the finger toward the tip to build a large, round drop. Pause between squeezes and re-warm if the flow slows.

Note: Do not squeeze too hard. Over-squeezing pushes tissue fluid into the sample and dilutes the blood, which can make the sample unusable even if you reach the target volume.

If you cannot fill the target

  1. Re-warm your hand and gently massage the finger again.

  2. If needed, prick a different finger — the middle or ring finger of your non-dominant hand works best.

  3. If you still cannot fill the target after two or three attempts, stop collecting. Continuing to force it usually makes the sample worse.

Need more help?

After three unsuccessful attempts, 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.

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