Should nurses wipe away the first drop of blood during capillary blood glucose (CBG) testing, or can they apply it directly to the glucose test strip? This familiar nursing procedure has traditionally been taught with a simple instruction: discard the first drop and use the second. However, evidence from studies comparing the two drops challenges the idea that discarding the first drop is always necessary for glucose monitoring.
The answer depends on how the skin was prepared, whether the hands are clean, the possibility of external contamination, and the instructions for the specific glucose meter. Understanding these factors helps nurses distinguish a traditional procedural habit from a practice supported by evidence.
Clinical Question: Does the First Drop Need to Be Discarded?
PICO question: In patients undergoing capillary blood glucose monitoring, does using the first drop of blood, compared with wiping it away and using the second drop, produce comparable glucose measurements when appropriate skin preparation is performed?
Quick Answer
Not necessarily. When the hands have been washed with soap and water and thoroughly dried, evidence supports using the first drop of blood for routine glucose monitoring, provided the glucose meter's instructions permit it. However, when the hands cannot be washed, the skin is contaminated, or the sampling method requires a different approach, wiping away the first drop and using the second may be appropriate. Nurses must distinguish glucose monitoring from other capillary blood collection procedures and follow the applicable device instructions and institutional protocol.
- Wiping away the first drop is not universally necessary for capillary blood glucose monitoring.
- Clean hands and thorough drying are important for reliable glucose measurements.
- Sugar-containing substances on the fingers can cause falsely elevated readings.
- A systematic review and meta-analysis found no statistically significant overall difference between first-drop and second-drop glucose measurements.
- Follow the glucose meter manufacturer's instructions and the facility's approved procedure.
Why Do Nurses Traditionally Wipe the First Drop of Blood?
The conventional practice of discarding the first drop comes from concerns about contamination of capillary blood samples. The first drop may contain material from the skin surface, including debris, and may be affected by tissue fluid or substances left on the finger.
General capillary blood sampling guidance from the World Health Organization recommends wiping away the first drop because of the potential for contamination by tissue fluid or debris from the skin.[1]
However, a critical distinction exists between collecting a specimen for laboratory analysis and obtaining a drop of blood for glucose measurement using a specific point-of-care device. Recommendations developed for general capillary blood sampling should not automatically be interpreted as a universal requirement for every glucose meter.
Glucose monitoring also has a specific contamination concern: glucose-containing substances on the fingers can affect the reading. For example, residue from fruit or fruit juice may produce a falsely elevated glucose result if the finger is not cleaned properly.
Consequently, the most important question is not simply whether the first drop should be discarded. Nurses should first determine whether the skin has been appropriately prepared and whether the sampling method is consistent with the meter's instructions.
What Does the Evidence Say About the First Drop Versus the Second Drop?
1. Systematic Review and Meta-Analysis: Evidence From 23 Studies
Dong and colleagues published a systematic review and meta-analysis examining whether the first or second drop of capillary blood produces different glucose measurements.[2]
The researchers searched multiple databases, including PubMed, ClinicalTrials.gov, the Cochrane Library, EMBASE, and several Chinese databases. Their search included studies published up to November 10, 2023.
Study design: Systematic review and meta-analysis.
Sample: Twenty-three studies involving 3,121 patients.
Main findings: The pooled analysis found no statistically significant difference between first-drop and second-drop glucose measurements. The reported mean difference was -0.01, with a 95% confidence interval of -0.04 to 0.03 and a p-value of 0.73. Subgroup analyses also found no statistically significant differences according to the glucose meters and skin-cleaning methods examined.
Clinical interpretation: These findings challenge the assumption that the first drop must always be discarded during glucose monitoring. They support the use of the first drop when appropriate preparation and device instructions permit it.
Limitations: A pooled result showing no statistically significant difference does not prove that every first-drop measurement is interchangeable with every second-drop measurement. The included studies may differ in their populations, procedures, devices, and study quality. The results also do not eliminate the importance of preventing contamination or following device-specific instructions.
Evidence level: Johns Hopkins Level I is generally appropriate for a systematic review of experimental studies. However, the exact evidence level of this review should be assigned only after examining the designs and quality of its included studies.
The review is particularly relevant to nursing education because it evaluates the actual question being debated: whether discarding the first drop improves the glucose measurement compared with using it directly.
2. Clinical Study: What Happens When Hands Are Not Washed?
A clinical study published in Diabetes Care investigated how handwashing, contamination, and the choice of blood drop affected self-monitored glucose measurements.[3]
Study design: Comparative experimental study involving people performing capillary glucose measurements under different conditions.
Sample: The study included separate groups of 123 and 100 participants across its experimental conditions.
Main findings: When hands were not washed, glucose readings differed from control measurements by at least 10% in 11% of participants using the first drop and 4% using the second drop. When fingers had been exposed to fruit, the corresponding proportions were 88% and 11%.
The researchers concluded that washing hands with soap and water, drying them, and using the first drop was the preferred approach. If washing was not possible and the hands were neither visibly dirty nor exposed to sugar-containing substances, wiping away the first drop and using the second was an acceptable alternative.
Clinical interpretation: The findings highlight the importance of skin preparation. They also show why a potentially contaminated first drop should not be treated as equivalent to a first drop obtained from clean, dry hands.
Limitations: The study examined specific experimental conditions, and its findings may not apply equally to every glucose meter, patient population, or hospital setting. Its findings should therefore be interpreted alongside current device instructions and institutional procedures.
Evidence level: The study's exact Johns Hopkins EBP level depends on its experimental design classification and should be verified against the full methods before assigning a definitive level.
3. World Health Organization Guidance: General Capillary Sampling
The World Health Organization's guidelines on drawing blood describe a general capillary sampling procedure that includes cleaning the site, allowing the alcohol to air-dry when used, puncturing the skin, wiping away the first drop, and avoiding excessive squeezing.[1]
This guidance provides an important safety principle: the first drop may be unsuitable when the collection method and specimen requirements create a risk of contamination.
However, the guidance addresses capillary blood sampling more broadly. It should not be used in isolation to conclude that every finger-stick glucose measurement must begin with discarding the first drop. Glucose monitoring requires consideration of the specific meter, its instructions, and evidence directly examining glucose measurements.
The distinction matters in nursing practice. A nurse collecting capillary blood for a laboratory specimen may be following a different procedure from a nurse using a glucose meter at the bedside.
First Drop or Second Drop? A Practical Comparison
| Clinical situation | Practical approach | Reason |
|---|---|---|
| Hands washed with soap and water and thoroughly dried | Use the first drop if permitted by the meter instructions and facility protocol. | Evidence supports using the first drop under appropriate conditions. |
| Hands potentially contaminated with fruit juice or other sugary substances | Wash with soap and water and dry thoroughly before testing. | External glucose contamination can cause falsely elevated readings. |
| Hands cannot be washed, but are not visibly dirty or exposed to sugar-containing substances | Wipe away the first drop and use the second only when supported by the device instructions and applicable protocol. | An alternative approach is supported by the comparative clinical study. |
| Alcohol used to prepare the puncture site | Allow the alcohol to dry completely and follow the device-specific procedure. | Residual liquid can interfere with specimen collection and measurement. |
| Capillary specimen collected for a different test | Follow the collection procedure for that test. | General capillary sampling recommendations may differ from glucose meter instructions. |
The comparison above summarizes evidence and general principles. It does not replace the manufacturer's instructions for the particular glucose meter or the facility's approved procedure.
Why Handwashing May Matter More Than Wiping the First Drop
When glucose measurements are unexpectedly high, external contamination should be considered before assuming that the patient's blood glucose has changed substantially.
Substances containing glucose may remain on the fingers after handling food. If a finger is punctured without adequate cleaning, the sample may contain enough external glucose to produce a misleading result. Wiping away the first drop may reduce this effect in some circumstances, but it is not a substitute for cleaning contaminated hands.
Washing and drying the hands addresses the contamination at its source. It also allows the nurse to use a standardized procedure rather than relying on the assumption that the second drop will always be more accurate.
The comparative study discussed earlier found that exposure to fruit was associated with substantial differences between test readings and control measurements. The findings reinforce the importance of appropriate hand preparation rather than focusing exclusively on which drop is collected.[3]
Implications for Nursing Practice
Assessment Before Testing
- Determine whether the patient's hands are clean and dry.
- Ask whether the patient has recently handled fruit, food, or other potentially contaminating substances when the result appears inconsistent with the clinical picture.
- Check that the meter and test strips are appropriate for use and that the strips are stored according to the manufacturer's instructions.
- Review the device instructions and the facility's procedure for obtaining a capillary blood glucose measurement.
Intervention During Sampling
- Perform hand hygiene and use the appropriate protective equipment.
- Clean the patient's hands as indicated and ensure that they are thoroughly dry.
- Use a new, single-use lancet for each finger-stick procedure.
- Allow blood to form without excessive squeezing or forceful milking of the finger.
- Apply the blood sample to the strip according to the meter manufacturer's instructions.
- If the procedure requires discarding the first drop, use clean gauze or an appropriate single-use material.
Monitoring and Documentation
- Document the glucose result and any relevant circumstances affecting the measurement according to institutional policy.
- Assess whether the result is consistent with the patient's symptoms, clinical condition, and previous readings.
- Repeat the measurement or obtain a laboratory glucose measurement when clinically indicated and in accordance with the applicable protocol.
- Document corrective actions when a potentially contaminated or technically unreliable sample is suspected.
The nurse should not delay urgent assessment or treatment of suspected hypoglycemia or severe hyperglycemia solely to settle a procedural question about which blood drop should be used. Clinical urgency and the facility's emergency protocol take priority.
The evidence suggests that discarding the first drop is not inherently necessary for every capillary blood glucose measurement. The quality of the sample depends on the entire procedure, including skin preparation, avoidance of contamination, appropriate blood collection, and adherence to device instructions. Nurses should evaluate the rationale behind each procedural step rather than applying a general capillary sampling rule without considering its intended use.
Bedside Checklist: Should the First Drop Be Wiped Away?
Before collecting the sample, use the following decision guide.
- Identify the test. Confirm that the procedure is capillary blood glucose monitoring rather than another form of capillary specimen collection.
- Check the protocol. Review the meter instructions and institutional procedure.
- Assess hand cleanliness. If contamination is possible, clean the hands appropriately. Wash with soap and water when indicated, particularly after exposure to sugary substances.
- Dry the skin. Ensure that the hands are thoroughly dry before puncturing.
- Follow the specified sampling method. Use the first drop when the approved procedure permits it. Otherwise, discard the first drop and use the next one as directed.
- Collect the sample correctly. Avoid excessive squeezing and apply the sample to the strip as instructed.
- Evaluate unexpected results. If the result does not fit the clinical picture, investigate possible sampling or device errors and repeat testing when appropriate.
Hypothetical Example
A nurse obtains a capillary blood glucose reading that is substantially higher than the patient's recent measurements. The patient reports having handled sliced fruit shortly before the test. Instead of immediately interpreting the result as a sudden deterioration in glycemic control, the nurse considers possible contamination, cleans and dries the patient's hands, and repeats the measurement according to the facility's protocol.
This example illustrates why the sampling process matters. A repeat measurement obtained under appropriate conditions can help determine whether the initial result was reliable, while clinical assessment determines whether additional action is required.
Barriers and Considerations in Clinical Settings
Practice may differ between hospitals, outpatient clinics, emergency departments, and home glucose monitoring. These differences can reflect the type of device used, the availability of handwashing facilities, the clinical condition of the patient, and local procedural requirements.
In emergency settings, time-sensitive decisions may need to be made before ideal sampling conditions are available. Nurses should follow the approved emergency procedure and consider confirmatory testing when a result is questionable. A patient with symptoms suggesting a glucose emergency requires timely clinical assessment, not an unnecessary delay while staff debate a routine sampling step.
Training also matters. If staff members have learned different methods, inconsistent procedures can develop across shifts. Nursing educators can address this by reviewing the current evidence, checking the instructions for the meters actually used in the facility, and standardizing practice through an approved protocol.
In the Philippines, nurses should follow their institution's approved procedures and applicable professional requirements. International research can inform local practice, but implementation should account for the equipment and protocols used in the specific clinical setting.
Gaps in the Evidence and Future Research
Although the available systematic review supports using the first drop for glucose monitoring under appropriate conditions, several questions remain relevant to nursing practice.
- Different patient populations: Further research could clarify whether results are consistent across children, older adults, critically ill patients, and other groups with different sampling challenges.
- Different glucose meters: Studies should continue evaluating whether findings apply consistently across devices and test-strip technologies.
- Real-world hospital procedures: Additional studies could examine how sampling methods perform under routine clinical conditions, including emergency departments and inpatient wards.
- Clinical outcomes: Research should examine whether standardizing first-drop procedures meaningfully improves clinical decisions, reduces repeat testing, or changes patient outcomes.
These gaps do not mean that the available evidence is unusable. Rather, they highlight the need to interpret findings within the conditions and populations studied.
Red Flags: When to Reassess a Glucose Reading
- The glucose result is inconsistent with the patient's symptoms or clinical presentation.
- The fingers may have been contaminated by food, fruit juice, or other substances.
- The sample was insufficient, improperly applied, or collected using an incorrect procedure.
- The meter displays an error or quality-control concerns are identified.
- The patient has symptoms concerning for severe hypoglycemia or hyperglycemia.
Reassess the patient, repeat testing or obtain confirmatory testing as clinically indicated, and follow the applicable emergency or escalation protocol. Do not delay urgent treatment when the clinical situation requires immediate action.
Frequently Asked Questions
1. Is it necessary to wipe the first drop of blood during CBG testing?
Not always. Evidence supports using the first drop for routine glucose monitoring when the hands have been washed and thoroughly dried, provided the meter instructions and facility protocol permit it. Wiping the first drop may be appropriate in other circumstances, including when the approved procedure requires it or when handwashing is unavailable and the alternative method is supported.
2. Why do nursing instructors teach students to discard the first drop?
The practice is based partly on concerns about contamination from skin debris and tissue fluid during capillary blood collection. However, general capillary sampling guidance does not automatically apply to every glucose meter. Research specifically examining glucose monitoring indicates that the first drop can be used under appropriate conditions.
3. Can using the first drop cause a falsely high blood glucose reading?
It can be affected by contamination, particularly when the finger has been exposed to glucose-containing substances such as fruit juice. However, the concern is not that the first drop is inherently inaccurate. Appropriate handwashing and drying are essential, and unexpected readings should be reassessed according to the clinical situation and device instructions.
4. Should the first drop be wiped away if alcohol is used?
Follow the instructions for the glucose meter and the facility's approved procedure. If alcohol is used, allow it to dry completely before puncturing the skin. Whether the first drop should be discarded depends on the specified sampling method. Alcohol use alone should not be treated as a universal reason to discard the first drop for every glucose meter.
5. Is wiping the first drop necessary for all capillary blood tests?
No universal rule should be applied to every capillary specimen. General capillary blood collection guidance may recommend discarding the first drop to reduce contamination, while glucose monitoring evidence supports using the first drop under appropriate conditions. The correct method depends on the test, collection device, and applicable protocol.
6. What should a nurse do if the glucose result does not match the patient's condition?
Assess the patient and consider sampling errors, skin contamination, device problems, and other relevant factors. Repeat the measurement using the approved procedure or obtain confirmatory testing when indicated. If the patient has signs of a glucose emergency, follow the appropriate escalation and treatment protocol without unnecessary delay.
In Plain Language
You do not always need to wipe away the first drop of blood when checking blood sugar with a finger-stick meter. Research suggests that the first drop can be used when the hands are clean and dry and the meter's instructions allow it. If the fingers may be contaminated, wash and dry them before testing. Always follow the instructions for the specific meter and the procedure approved by the healthcare facility.
Conclusion: Should Nurses Still Wipe the First Drop of Blood During CBG?
The question of whether to discard the first drop of blood during capillary blood glucose monitoring deserves an evidence-based answer rather than an automatic yes or no. A systematic review and meta-analysis found no statistically significant overall difference between first-drop and second-drop glucose measurements. An earlier clinical study also emphasized that hand cleanliness and contamination can influence results.
For nurses, the practical priority is to obtain a reliable measurement using an appropriate, standardized procedure. Clean and dry hands, correct sample collection, device-specific instructions, and clinical reassessment of unexpected readings all contribute to safe glucose monitoring.
Review the procedure used in your clinical area and discuss the supporting evidence with your nursing educator or evidence-based practice committee. The goal is not simply to preserve or abandon a traditional step, but to ensure that every step has a clear clinical rationale.
Disclaimer
This article is for educational purposes only. It does not replace institutional policies, clinical guidelines, professional judgment, or individualized medical advice. Always follow your facility's protocols and consult current guidelines. Members of the public should consult a qualified healthcare provider about any medical condition.
References
- World Health Organization. (2010). WHO guidelines on drawing blood: Best practices in phlebotomy. World Health Organization. https://www.ncbi.nlm.nih.gov/books/NBK138654/ [Guideline] ↩
- Dong, X., Zhang, C., Wu, T., & Zhu, B. (2024). First versus second drop of capillary blood for monitoring blood glucose: A meta-analysis and systematic review. Archives of Medical Science, 20(6), 1909–1917. https://doi.org/10.5114/aoms/186657 [Systematic review and meta-analysis] ↩
- Hortensius, J., Slingerland, R. J., Kleefstra, N., Logtenberg, S. J. J., Groenier, K. H., Houweling, S. T., & Bilo, H. J. G. (2011). Self-monitoring of blood glucose: The use of the first or the second drop of blood. Diabetes Care, 34(3), 556–560. https://doi.org/10.2337/dc10-1694 [Comparative experimental study] ↩
Last updated: October 2026
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