On Call Extra Re-Dosing & Second Blood Sample Guide

On Call Extra re-dosing second blood drop within 3 seconds guide for insufficient sample

One of the useful features of the On Call Extra Blood Glucose Monitoring System is its ability to accept an additional blood sample when the first drop is insufficient.

This feature is commonly called re-dosing or second blood-drop application.

Under the manufacturer's specified conditions, the On Call Extra system allows a second blood drop to be applied within approximately 3 seconds when the first application is insufficient and the meter has not yet started its normal countdown.

This guide explains exactly when re-dosing is allowed, when you should not add more blood, how it relates to the E-5 error, and when you should discard the strip and start again.

For the complete On Call Extra system guide, read: On Call Extra Glucometer & Test Strips Complete Guide .

What Is On Call Extra Re-Dosing?

Re-dosing means applying a second blood drop to the same On Call Extra Test Strip when the first sample does not completely fill the strip as required.

The feature is designed to help reduce unnecessary strip wastage when the first blood application is slightly insufficient.

The key rule is:

If the first blood sample has been applied but the countdown has not started, a second blood drop may be applied within approximately 3 seconds.

This is a short, controlled re-dosing opportunity. It is not unlimited re-application of blood.

On Call Extra Re-Dosing: Quick Rule

Situation	What to Do
First blood drop applied and check window fills correctly	Allow the meter to begin testing. No second drop is needed.
First blood drop insufficient and countdown has NOT started	Apply a second drop within approximately 3 seconds.
Countdown has already started	Do not add more blood.
Check window is incomplete but countdown has started	Discard the strip and repeat with a new strip.
Re-dosing is attempted too late	E-5 or an unreliable test may occur.

Why Does On Call Extra Have a Re-Dosing Feature?

The standard On Call Extra system requires only approximately 0.4 µL of fresh capillary whole blood.

Even with this small sample requirement, the first blood drop may occasionally be too small to completely fill the strip's reaction area.

Rather than immediately discarding the strip, the Extra system provides a short opportunity to add a second sample when the meter has not yet started the test countdown.

This can help avoid wasting a strip because of a slightly insufficient first sample.

When Can You Add a Second Blood Drop?

A second drop can be considered when all of the following apply:

you are using a compatible On Call Extra Test Strip,
the strip is correctly inserted,
the meter was ready for blood before the first sample was applied,
the first sample entered the sample tip,
the strip did not receive enough blood to begin normal testing, and
the meter's countdown has not started.

In this situation, apply the additional blood sample promptly within the approximately 3-second re-dosing window.

When Should You NOT Add More Blood?

Do not add a second sample if the meter has already started its countdown.

Once the countdown begins, the meter has started processing the sample. Adding more blood at that point can interfere with the intended testing procedure.

If the check window is not completely filled but the countdown has already started:

Do not add more blood.
Allow the failed test procedure to end or follow the displayed instruction.
Discard the affected strip.
Insert a new compatible On Call Extra Test Strip.
Repeat the test from the beginning.

The 3-Second Re-Dosing Window

The manufacturer's guidance describes a re-dosing capability within approximately 3 seconds.

This short time window is important because re-dosing is intended to complete an initially insufficient sample before the normal test has begun.

Do not wait several seconds, reconsider the sample and then attempt to add more blood after the testing sequence has already progressed.

If there is doubt about whether the permitted window has passed, using a new strip and restarting the test is preferable to continuing to add blood to the existing strip.

How to Re-Dose an On Call Extra Strip Correctly

If the first blood sample is insufficient and the countdown has not started:

Keep the test strip correctly inserted in the meter.
Obtain an additional adequate blood drop promptly.
Bring the blood drop to the sample tip at the end of the test strip.
Allow the strip to draw in the additional sample.
Complete this additional application within approximately 3 seconds.
Watch the strip's check window.
Once the meter recognises an adequate sample, allow it to begin the countdown.
Do not add any further blood after the countdown begins.

Where Should the Second Blood Drop Be Applied?

The second sample should be applied to the same sample tip at the end of the On Call Extra Test Strip.

Do not apply the additional blood:

to the top surface of the strip,
to the back of the strip,
directly over the check window,
onto the contact bars, or
by smearing blood along the strip.

The strip is designed to draw blood through the sample tip into its reaction cell.

What Is the Check Window?

The check window on the On Call Extra Test Strip helps show whether enough sample has entered the strip.

After applying the blood drop to the sample tip, allow the sample to fill the check window as instructed.

If the check window fills adequately, the meter should begin its testing countdown.

If it does not fill and the countdown has not begun, the re-dosing feature may be used within the permitted window.

What If the Check Window Is Only Partly Filled?

There are two different situations:

Countdown has NOT started

A second blood drop may be applied within approximately 3 seconds to complete the sample.

Countdown HAS started

Do not add more blood.

If the meter begins counting down before the check window is adequately filled, discard the strip and repeat the procedure with a new test strip.

On Call Extra E5 and Re-Dosing

The E-5 error is closely related to insufficient sample and incorrect or late re-dosing.

E-5 may occur when:

too little blood was initially applied,
the strip did not fill correctly,
additional blood was applied after the permitted re-dosing period, or
blood was added after the meter had already begun its countdown.

If E-5 appears, do not repeatedly add more blood to the same failed strip.

Follow the manufacturer's troubleshooting instructions and use a fresh strip when directed.

For the complete error guide:

On Call Extra Error Codes & Troubleshooting Guide →

What If the First Blood Drop Is Very Small?

If the first sample is obviously too small and the meter does not begin the countdown, obtain an additional blood drop promptly and apply it within the permitted re-dosing window.

Avoid repeatedly squeezing or milking the fingertip excessively merely to produce additional sample.

If obtaining an adequate blood drop is consistently difficult, review:

lancing-device depth,
lancet condition,
hand warmth,
testing technique, and
the instructions supplied with the lancing device.

Can You Add a Third Blood Drop?

The manufacturer's re-dosing feature is described as allowing a second blood drop within approximately 3 seconds.

It should not be interpreted as permission to add repeated third, fourth or additional samples until the strip eventually fills.

If the first and permitted second application do not result in a proper test, discard the strip and restart with a new strip.

Can Blood Be Added After the 4-Second Test Starts?

No.

The approximately 4-second result time begins after the meter has accepted the sample and started its countdown.

Once that process has begun, do not apply more blood to the strip.

Can You Remove the Strip and Add More Blood?

No.

Do not remove the test strip during an active test in order to add more blood and then reinsert it.

Removing the strip during testing can itself cause an E-2 error.

If the strip must be removed because testing failed, discard it and restart with a new strip.

Can You Re-Dose an Already Used Test Strip?

No.

The On Call Extra Test Strip is a single-use diagnostic test strip.

Re-dosing refers only to adding a permitted second blood sample during the same initial test procedure.

It does not mean that a strip can be reused after a result has already been produced.

Does Re-Dosing Work with Every Glucometer?

No.

Do not assume that another glucose meter allows the same procedure simply because On Call Extra does.

Re-dosing rules are model-specific.

For example, the testing procedure for traditional On Call Plus should be followed according to the Plus-specific manufacturer instructions rather than automatically applying the Extra re-dosing procedure.

For the differences between the systems:

On Call Plus vs On Call Extra Glucometer Comparison →

Why On Call Extra Re-Dosing Can Reduce Strip Waste

Without a re-dosing feature, an insufficient initial sample can result in a failed test that requires an entirely new strip.

On Call Extra provides a brief opportunity to complete the sample before testing begins.

This can help avoid wasting a compatible strip when:

the initial drop was only slightly too small, and
additional blood can be applied promptly within the permitted window.

The feature should still be used exactly as intended rather than as a way to continue adding blood indefinitely.

How to Reduce Insufficient-Sample Problems

Correct technique can reduce how often re-dosing is required.

Wash and thoroughly dry your hands.
Warm cold hands gently before testing.
Use a new sterile lancet.
Set the lancing-device depth appropriately.
Allow an adequate blood drop to form before contacting the strip.
Touch the blood to the sample tip rather than smearing it.
Keep the sample against the tip until the strip fills.
Watch for the countdown to begin.

For the full procedure:

How to Use On Call Extra Glucometer & Test Strips →

Does Foil-Packed On Call Extra Support the Same Testing Principle?

Where the individually foil-packed strip is genuinely specified as compatible with the On Call Extra system, follow the testing and sample-application instructions supplied with that product.

Packaging format does not by itself change the requirement to:

use the correct On Call Extra strip,
apply blood to the sample tip,
fill the check window correctly, and
follow the Extra-specific re-dosing procedure.

For strip compatibility:

On Call Extra Test Strip Compatibility Guide →

Re-Dosing Does Not Correct a Compatibility Problem

If the wrong test-strip family has been inserted, adding more blood will not make the strip compatible.

Always begin with:

On Call Extra meter + compatible On Call Extra Test Strip.

If the meter displays an incorrect-strip error, remove the strip and verify the product before continuing.

Re-Dosing Does Not Correct an Expired or Damaged Strip

The re-dosing feature should not be used as a way to compensate for:

expired strips,
damaged strips,
contaminated strips,
improperly stored strips, or
strips from damaged packaging.

Use a fresh, compatible and appropriately stored strip.

For expiry and storage guidance:

On Call Extra Test Strips Expiry & Storage Guide →

Re-Dosing vs Audible Fill Detection

On Call Extra also includes audible fill detection.

Where the audio feature is enabled, the meter can provide an audible indication when sufficient sample has been accepted and measurement has started.

This can help users recognise that the sample has been accepted.

Once the meter has accepted the sample and started measuring, do not add more blood.

Re-Dosing and the 4-Second Result Time

The standard Extra meter provides a result in approximately 4 seconds after an adequate sample has been accepted.

The re-dosing window occurs before that normal test countdown begins.

Think of the sequence as:

Apply first blood sample.
Check whether the meter begins counting down.
If not, apply a permitted second drop promptly.
Once the meter accepts enough sample, countdown begins.
Do not add more blood.
Result appears in approximately 4 seconds.

What If the Meter Still Does Not Start After the Second Drop?

If the allowed second sample has been applied but the strip still does not begin the normal testing sequence:

do not keep adding more blood,
do not remove and reinsert the same strip,
note any displayed error code,
discard the failed strip, and
repeat with a new compatible strip.

If the problem repeatedly occurs across multiple fresh strips, review the testing technique and use the troubleshooting guide.

On Call Extra Troubleshooting Guide →

Quick Re-Dosing Checklist

Before adding a second blood drop, confirm:

the meter is On Call Extra,
the strip is compatible with On Call Extra,
the first sample has already been applied,
the sample is insufficient,
the countdown has not started,
the 3-second window has not passed, and
the additional sample will be applied to the strip's sample tip.

If these conditions are not met, restart with a new strip according to the manufacturer instructions.

Frequently Asked Questions

Can I add more blood to an On Call Extra Test Strip?

Yes, under the manufacturer's specified conditions. If the first sample is insufficient and the countdown has not started, a second blood drop may be applied within approximately 3 seconds.

How long do I have to add the second blood drop?

The On Call Extra re-dosing window is approximately 3 seconds.

Can I add blood after the countdown starts?

No. Once the countdown has begun, do not add more blood. If the strip has not filled correctly, discard it and repeat the test with a new strip.

What happens if I add blood too late?

Late re-dosing can result in an E-5 message or an inaccurate test result.

What does E5 mean on On Call Extra?

E-5 can be associated with insufficient sample or incorrect/late additional blood application. Follow the troubleshooting procedure and use a fresh strip when required.

Can I apply a third drop of blood?

The manufacturer describes re-application of a second blood drop within the short permitted window. Do not repeatedly add additional drops. Restart with a new strip if the test does not proceed correctly.

Where should the second blood drop be applied?

Apply it to the sample tip at the end of the test strip, not to the top, back, check window or contact bars.

How do I know if the first sample is sufficient?

The strip's check window should fill correctly and the meter should begin its testing countdown. Audible fill detection may also indicate that the meter has accepted sufficient sample when the audio feature is enabled.

Can I remove the strip and put it back after adding more blood?

No. Removing the strip during testing can cause an error. If the test has failed, use a new strip.

Can I reuse an On Call Extra strip?

No. On Call Extra glucose test strips are single-use diagnostic consumables. Re-dosing refers only to the permitted second sample during the same initial test.

Does On Call Plus have the same 3-second re-dosing feature?

Do not apply the Extra procedure to an On Call Plus meter. On Call Plus is a different system and should be operated according to its own instructions.

Does the foil-packed On Call Extra strip support re-dosing?

Where the foil-packed product is specifically intended for the On Call Extra system, follow the testing and re-dosing instructions supplied with that exact strip product.

Related On Call Extra Guides

Shop On Call Extra Test Strips

View the complete range: Shop On Call Extra Glucometers & Test Strips →

Medical information notice: This article explains the On Call Extra sample re-dosing feature and general test-strip operation. It does not replace the user manual supplied with your specific meter and strips, diagnose a medical condition or interpret an individual glucose result.

Follow the manufacturer's instructions for sample application, re-dosing and repeat testing. Your healthcare professional should determine your testing frequency, glucose targets and treatment plan.

If a glucose result is unexpectedly high or low, repeat the test according to the manufacturer's instructions where appropriate. Repeated extreme readings, severe symptoms, confusion, loss of consciousness or inability to self-treat require prompt medical assessment. Do not delay necessary medical care while investigating a sample-application problem.

On Call Extra Re-Dosing Guide: How to Apply a Second Blood Drop Correctly