Good Laboratory Notebook Practices for Biology Students

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-08-11

Introduction to Good Laboratory Notebook Practices

A laboratory notebook is the primary, contemporaneous record of your experimental work. It is a bound, sequentially paginated document in which you record your hypotheses, experimental designs, protocols, raw data, observations, calculations, and interpretations at the time the work is performed. In molecular biology, where experiments often involve multi-step procedures such as polymerase chain reaction (PCR), restriction enzyme digestion, or bacterial transformation, the notebook serves as the only reliable record of exactly what you did, with which reagents, at what concentrations, and under what conditions.

Purpose of a Laboratory Notebook

The laboratory notebook serves multiple interconnected purposes. First, it is a memory aid. A typical cloning experiment might involve a PCR amplification with a specific annealing temperature, a gel electrophoresis run at a particular voltage, and a ligation reaction with a defined insert-to-vector molar ratio. These parameters are impossible to recall reliably weeks or months later. Second, the notebook is a communication tool. When you join a lab, when you collaborate with colleagues, or when you write a manuscript, the notebook is the definitive source of experimental detail. Third, the notebook is a legal document. In academic research, it establishes priority of discovery. In industrial or patent-related contexts, it can determine the outcome of intellectual property disputes. Fourth, the notebook is a teaching tool. Reviewing your own entries allows you to identify patterns, troubleshoot failed experiments, and refine your techniques.

Legal and Ethical Importance

In the United States, patent law operates on a first-to-file basis, but a well-maintained notebook remains critical for establishing conception and diligence in interference proceedings and for defending against claims of derivation. In clinical or regulated research, the notebook is a component of Good Laboratory Practice (GLP) compliance, which mandates specific documentation standards. Beyond legal considerations, there is an ethical dimension. Scientific integrity rests on the accurate reporting of methods and results. A notebook that is incomplete, misleading, or falsified undermines the reproducibility of research and constitutes scientific misconduct. Fabricating data, omitting negative results, or altering entries after the fact are serious violations of research ethics. Your notebook is your scientific conscience on paper.

Core Principles of Notebook Documentation

Four principles govern all good laboratory notebook practices: permanence, completeness, accuracy, and traceability. These principles are not arbitrary rules; they exist to ensure that your record is trustworthy, durable, and legally defensible.

Permanent Ink and Bound Notebooks

Use a bound notebook with numbered pages, never a loose-leaf binder or spiral notebook from which pages can be removed. The binding ensures that pages cannot be inserted or removed without visible damage. Write in permanent black or blue ink. Black ink is preferred because it photocopies and scans with the highest contrast. Never use pencil, which can be erased, or water-soluble markers, which can smudge or be washed away. Never use correction fluid, correction tape, or erasers. The goal is a permanent, unalterable record. If you work in a laboratory that uses electronic notebooks, the same principles apply, but the medium differs; for a comparison of approaches, see Electronic Notebook Table Best Practices.

Writing in Real Time

Record your work at the moment you perform it, not at the end of the day, not the next morning, and certainly not at the end of the week. Contemporaneous recording is a core tenet of GLP Good Laboratory Practice. If you wait, you will forget details. You will forget that the water bath was set to 42°C instead of 37°C, that you added 2 µL of enzyme instead of 1 µL, or that the centrifuge was unbalanced. Write the entry before you start the experiment, and update it as you go. If you prepare a master mix for a 25 µL PCR reaction containing 1× Taq buffer, 200 µM each deoxynucleotide triphosphate (dNTP), 0.5 µM each primer, and 1 unit (U) of Taq DNA polymerase, record that information while you are pipetting, not after the thermal cycler has finished.

Recording Negative Results

A failed experiment is still data. A PCR that produced no amplicon, a transformation that yielded no colonies, a protein purification that gave no detectable protein—these outcomes are informative. They tell you that a condition was wrong, a reagent was degraded, or a protocol needs modification. Recording negative results prevents you and others in the laboratory from repeating the same mistake. It also provides a complete picture of your research trajectory. A notebook that contains only successful experiments is a falsified document. The absence of a band on an agarose gel is a result; record it, including the gel image or a careful drawing, and note your interpretation of why the reaction failed.

Structuring Your Notebook Entries

Each notebook entry should follow a consistent, logical structure. This consistency makes it easier for you to find information later and for others to read your notebook. A standard entry includes header information, a procedure, raw data, and conclusions.

Header Information

Begin every entry with the date. Use a format that cannot be ambiguous, such as "2025-06-14" or "14 June 2025." Include the experiment title, which should be descriptive enough to identify the work without reading the entire entry. For example, "PCR amplification of the lacZ gene from pUC19" is better than "PCR." If you are continuing an experiment from a previous day, note the page number of the earlier entry. Include the objective or hypothesis: what question are you asking, or what are you trying to construct? For example, "Objective: To amplify the 3,075-base pair (bp) lacZ coding sequence from pUC19 using primers LacZ-F and LacZ-R, introducing 5' *Bam*HI and 3' *Hind*III restriction sites for subsequent cloning into pET28a."

Procedure and Protocol Details

Record the procedure in sufficient detail that another scientist with standard training could reproduce it without asking you questions. This does not mean transcribing the entire protocol from a published paper, but it does mean recording the specific conditions you used. For a PCR, record the template DNA concentration (e.g., 10 ng/µL), the primer sequences or a reference to them, the final primer concentration, the polymerase and buffer used, the thermal cycling parameters (initial denaturation 95°C for 2 minutes; 30 cycles of 95°C for 30 seconds, 58°C for 30 seconds, 72°C for 90 seconds; final extension 72°C for 5 minutes), and the expected product size. For a restriction digest, record the DNA amount (e.g., 1 µg), the enzyme (e.g., *Bam*HI-HF), the buffer (e.g., CutSmart Buffer, 1×), the reaction volume (e.g., 50 µL), the incubation temperature (37°C), and the duration (1 hour). Note any deviations from the written protocol. If you used a kit, record the kit name, catalog number, and lot number.

Data and Observations

Record all raw data directly in the notebook. This includes spectrophotometer readings, gel images (photographed or drawn), colony counts, cell densities, and any qualitative observations such as color changes, precipitation, or unexpected turbidity. Record the instrument settings and the units. If you measure the optical density at 600 nm (OD₆₀₀) of an Escherichia coli culture, record the value and the dilution factor if the reading was above the linear range of the instrument (typically above 0.8). If you run a DNA ladder on a gel, record the ladder name and the sizes of the relevant bands. Do not rely on memory or on scraps of paper.

Conclusions and Next Steps

At the end of the entry, write a brief conclusion. What did you learn? Did the experiment succeed or fail? What is your interpretation of the results? What will you do next? For example, "The PCR produced a single amplicon of approximately 3.1 kb, consistent with the expected lacZ product. The band was excised and purified using the QIAquick Gel Extraction Kit. Next step: restriction digest of the purified PCR product and pET28a vector with *Bam*HI-HF and *Hind*III-HF, followed by ligation." This section turns your notebook from a passive record into an active tool for planning.

Data Recording and Integrity

The integrity of your data depends on how you record it. Raw data are the unprocessed, direct measurements from your instruments. Processed data are the results of calculations or analyses applied to raw data. Both have a place in the notebook, but they must be clearly distinguished.

Raw Data vs. Processed Data

Record raw data first, exactly as obtained. If you use a spectrophotometer to measure the absorbance of a DNA sample at 260 nm (A₂₆₀) and 280 nm (A₂₈₀), record those values. Then, in a separate section or clearly labeled calculation, compute the DNA concentration using the extinction coefficient (e.g., 50 ng/µL per A₂₆₀ unit for double-stranded DNA) and the A₂₆₀/A₂₈₀ ratio to assess purity. Do not record only the final concentration; the raw absorbance values are the primary data. Similarly, if you count 45 colonies on a plate from a 10⁻⁶ dilution of a transformation, record the colony count and the dilution, then calculate the transformation efficiency in colony-forming units per microgram (cfu/µg) of plasmid DNA.

Using Tables and Graphs

Tables are an efficient way to record repetitive data. When you use a table, label the columns and rows clearly, include units in the headers, and record every value. For example, when measuring the growth curve of a bacterial culture, you might construct a table with time (minutes), OD₆₀₀, and notes. Graphs are useful for visualizing trends, but they should be drawn or printed and taped into the notebook, with the raw data table alongside. Never replace raw data with a graph; the graph is a representation, not the data itself. The table below shows a typical format for recording a series of PCR optimization reactions.

Handling Errors and Corrections

Errors in data recording are inevitable. The correct way to handle an error is described in detail in the section on corrections below. The key principle is that you must never obscure the original entry. A single line through the error, with the correction written nearby, is the standard. If you realize that a measurement was taken incorrectly, do not erase it. Draw a line through it, write "error—see page 45" or simply correct the value, and initial and date the correction.

Proper Use of Attachments and Loose Materials

Molecular biology generates a substantial amount of loose data: agarose gel photographs, autoradiographs, DNA sequencing chromatograms, spectrophotometer printouts, and protein gel images. These materials must be incorporated into the notebook in a way that preserves them and links them to the relevant experimental entry.

Taping and Pasting

The standard method is to affix the material to the notebook page using tape or glue. Use a good-quality transparent tape that will not yellow or degrade over time. Apply the tape along the entire edge of the printout, not just at the corners, to prevent it from catching and tearing. If you are taping a gel image, trim the excess paper so that it fits within the page margins. Write the figure number, the date, and a brief description directly on the printout before taping it in, or write this information in the notebook next to the taped item. For example, "Figure 1: 1% agarose gel of lacZ PCR products. Lane 1: 1 kb DNA ladder (NEB); Lane 2: reaction 1; Lane 3: reaction 2; Lane 4: reaction 3; Lane 5: negative control (no template)." If you use a thermal printer that produces paper with a waxy coating, note that these prints can fade over time; photocopy or scan them and tape the copy into the notebook.

Cross-Referencing with Notebook Page Numbers

Whenever you attach a loose item, cross-reference it with the page on which it is attached. In the body of the entry, write "See gel image on page 42." On the taped image itself, write "Page 42, entry dated 2025-06-14." This cross-referencing is essential for traceability. If a gel image is referenced in a later entry, note the page number of the original image. For example, "The purified lacZ PCR product (see gel, page 42) was digested with *Bam*HI-HF and *Hind*III-HF." This practice ensures that anyone reading the notebook can find all related data. For guidance on managing large volumes of loose data in a digital environment, see Duplicate Laboratory Notebook Best Practices.

Corrections and Amendments

Mistakes in a laboratory notebook are unavoidable. The way you correct them is a measure of your scientific integrity. The cardinal rule is: never obliterate the original entry.

Making Corrections

When you make an error, draw a single horizontal line through the incorrect text or value. The original entry must remain legible. Write the correct value or text nearby, in the margin or immediately above the struck-through entry. Add your initials and the date next to the correction. For example, if you wrote "37°C" but the correct temperature was "42°C," draw a line through "37°C," write "42°C" above it, and add your initials and the date. If you need to correct a value in a table, strike through the incorrect value and write the correct value in the same cell, or write a footnote at the bottom of the table. Never use correction fluid, correction tape, or an eraser. Never write over the original entry. Never tear out a page. If you make a substantial error and need to rewrite an entire page, do not remove the original page. Instead, write "VOID" diagonally across the page, leave it in the notebook, and continue on the next page.

Adding Supplementary Notes

Sometimes you will need to add information to an entry after it has been completed. This is acceptable, provided you do so clearly and honestly. Write the supplementary note in the margin or at the bottom of the page, draw a line to the relevant section, and add your initials and the date. For example, "Note added 2025-06-16: The *Bam*HI-HF enzyme used in this digest was from lot number X123, which was later found to be contaminated." If the supplementary note is long, write it on a new page and cross-reference it to the original entry. Never insert a note into the middle of an existing entry in a way that makes it appear to have been written at the same time.

Intellectual Property and Confidentiality

Your laboratory notebook is a legal document. In an academic setting, it establishes the date of conception of an invention or discovery. In an industrial setting, it is often the key evidence in a patent dispute. The notebook must therefore be maintained in a way that makes it legally credible.

Witnessing and Signatures

Many laboratories require that notebook entries be witnessed on a regular basis. A witness is a person who has read the entry and can attest that it was written by the named individual on the stated date. The witness signs and dates the page, often adding the phrase "Read and understood." This practice is particularly important for entries that describe a potentially patentable invention. The witness should be someone who is not a co-inventor, to avoid a conflict of interest. In an academic teaching laboratory, your instructor or a laboratory supervisor can serve as a witness. If your laboratory does not require witnessing, it is still good practice to have your notebook reviewed periodically by a supervisor.

Storing Notebooks

Keep your notebook in a secure location when it is not in use. Do not leave it on a bench where it could be damaged by spills or taken by someone else. When you leave a laboratory, the notebook typically remains the property of the laboratory or institution. If you are working in a commercial setting, the notebook is the property of the company. Never remove a notebook from the laboratory without permission. If you are working with proprietary reagents or unpublished data, be mindful of confidentiality. Do not discuss the contents of your notebook in public spaces, and do not share it with individuals outside your laboratory without authorization. For more on the broader framework of documentation in regulated environments, see Good Laboratory Practices for Clinical Labs.

Common Pitfalls and How to Avoid Them

Students consistently make the same documentation errors. Recognizing these pitfalls is the first step to avoiding them.

Pitfall: Writing on Loose Paper

The most common and most damaging habit is writing data on loose paper—a scrap of paper, a paper towel, the back of an envelope—with the intention of transferring it to the notebook later. This practice is unacceptable. Loose paper is easily lost, damaged, or destroyed. The transfer step introduces errors and creates an opportunity for data to be accidentally or deliberately altered. The solution is simple: always have your notebook at the bench. If you must make a temporary note, write it directly in the notebook, even if it is messy. You can clean it up later, but the data must be recorded in the notebook at the time of the experiment.

Pitfall: Using Pencil or Erasable Ink

Pencil is erasable, which is precisely why it is unacceptable for a permanent record. Erasable pens are equally problematic. The entire purpose of the notebook is to create an unalterable record. If you use pencil, you or someone else can erase a value and replace it with another, and there will be no evidence that the change occurred. This is a serious integrity issue. Always use permanent black or blue ink. If you are concerned about making mistakes, remember that the correct way to handle an error is to strike through it, not to erase it.

Pitfall: Vague Descriptions

Writing "Ran a gel" or "Did a PCR" is not documentation. It is a placeholder that provides no useful information. A reader of your notebook should be able to reproduce your experiment without asking you a single question. If you write "Ran a gel," you have not recorded the percentage of the agarose gel, the voltage, the running buffer, the DNA ladder, the stain, or the samples. Write "Ran a 1% agarose gel in 1× Tris-acetate-EDTA (TAE) buffer at 100 V for 45 minutes. Gel was stained with ethidium bromide (0.5 µg/mL). Loaded 5 µL of each PCR reaction mixed with 1 µL of 6× gel loading dye. Lane 1: 1 kb DNA ladder (New England Biolabs, catalog #N3232)." This level of detail is what is expected. If you are unsure how much detail to include, err on the side of more detail. A good rule of thumb is to write as if you are writing for a future student who has never performed the experiment before.

Pitfall: Delaying Entries

Writing up your notebook at the end of the day, or worse, at the end of the week, is a common but serious error. Memory is fallible. You will not remember the exact annealing temperature, the precise amount of enzyme, or the order in which you added reagents. You will also not remember the qualitative observations—the color of a culture, the viscosity of a solution, the unexpected smell—that can be critical for troubleshooting. Write in real time. If you are at the bench, keep the notebook open and write as you go. If you are using a protocol from a published paper, note the citation and then record any deviations as they occur.

Pitfall: Omitting Negative Results

It is human nature to want to record successes and forget failures. In science, this is a dangerous habit. Negative results are data. They prevent you and your colleagues from repeating failed experiments. They can also provide insight into the biology of your system. If a transformation fails, record it. Note the number of colonies (zero), the conditions, and your hypothesis for the failure (e.g., "Possible reason: ligation reaction may have failed due to low insert concentration; will repeat with a 3:1 insert-to-vector molar ratio"). A notebook that records only successes is a falsified document.

Pitfall: Poor Attachment of Loose Materials

Taping a gel image in by one corner, or taping it so that it covers other writing, is a common problem. The image will eventually tear or fall out. Tape the entire edge of the printout. Do not cover any existing writing. If the printout is larger than the page, trim it to fit. Write the figure number and description on the printout before taping, or write it in the notebook next to the taped item. For a detailed discussion of how to handle the wide variety of loose data generated in a molecular biology laboratory, see Molecular Cloning a Laboratory Manual.

Pitfall: Forgetting to Sign and Date

Every entry must be signed and dated. The date is the first line of the entry. The signature is typically placed at the end of the entry. If you make a correction, you initial and date the correction. If you add a supplementary note, you initial and date the note. The signature and date are what make the notebook a legal document. Without them, there is no way to establish who wrote the entry or when.

Practical Summary: Checklist for Every Entry

Use the following checklist to ensure that every notebook entry meets the standards of good laboratory notebook practices.

Pre-Experiment Checklist

Before you begin any experiment, confirm that you have the following in place:

• [ ] Bound notebook with numbered pages is available at the bench.
• [ ] You are writing in permanent black or blue ink.
• [ ] The date is written at the top of the page.
• [ ] The experiment title and objective are stated.
• [ ] The relevant protocol is cited, or the full procedure is written out.
• [ ] All reagents, including catalog numbers and lot numbers, are recorded.
• [ ] All instruments are calibrated and the settings are noted.

Post-Experiment Review

After you finish the experiment, review your entry to confirm that it is complete:

• [ ] All raw data are recorded directly in the notebook, not on loose paper.
• [ ] All calculations are shown, with units.
• [ ] All observations, including negative results, are recorded.
• [ ] All attachments (gel images, printouts) are taped in and labeled.
• [ ] All corrections are made with a single line through the error, with initials and date.
• [ ] A conclusion is written, and next steps are identified.
• [ ] The entry is signed and dated.

Frequently Asked Questions

Why is it important to use a bound notebook for lab work?

A bound notebook with numbered pages prevents the removal or insertion of pages without visible damage. This is essential for the integrity and legal credibility of the record. If pages can be removed, there is no way to prove that the notebook is a complete and unaltered record of the work. Loose-leaf binders and spiral notebooks do not provide this guarantee. The bound format is a simple, physical safeguard that supports the honesty and completeness of your scientific record.

Can I use pencil in my lab notebook?

No. Pencil is erasable, which means the record can be altered without a trace. The same applies to erasable pens. The laboratory notebook must be a permanent, unalterable document. Use permanent black or blue ink. If you make a mistake, draw a single line through the error and write the correction nearby, then initial and date the correction. This preserves the original entry while clearly indicating the change.

What should I do if I make a mistake in my notebook?

Draw a single horizontal line through the incorrect text or value. The original entry must remain legible. Write the correct information nearby, and add your initials and the date. Never use correction fluid, correction tape, or an eraser. Never write over the original entry. If you need to add a supplementary note after the entry is complete, write it in the margin or at the bottom of the page, draw a line to the relevant section, and initial and date the note.

How much detail should I include in my lab notebook?

Include enough detail that another scientist with standard training could reproduce your experiment without asking you questions. Record the exact reagents, including concentrations, volumes, catalog numbers, and lot numbers. Record the instrument settings and the duration of each step. Record all raw data and all calculations. Record your observations, including qualitative observations such as color changes or unexpected precipitation. When in doubt, include more detail, not less. A good rule of thumb is to write as if you are writing for a future student who has never performed the experiment before.

Do I need to record failed experiments?

Yes. A failed experiment is still data. It tells you that a condition was wrong, a reagent was degraded, or a protocol needs modification. Recording negative results prevents you and your colleagues from repeating the same mistake. It also provides a complete picture of your research trajectory. A notebook that contains only successful experiments is a falsified document. Record the failure, note the conditions, and state your hypothesis for why it failed and what you will do differently next time.

What is the best way to attach loose data like printouts?

Use a good-quality transparent tape and apply it along the entire edge of the printout, not just at the corners. Trim the printout to fit within the page margins. Write a figure number, the date, and a brief description directly on the printout before taping it in, or write this information in the notebook next to the taped item. Cross-reference the attachment with the page number in the body of the entry. If the printout is on thermal paper, which fades over time, photocopy or scan it and tape the copy into the notebook.

How often should I write in my lab notebook?

You should write in your notebook in real time, as you perform the experiment. Record the procedure before you start, and update the entry as you go. Record data at the moment you obtain it. Do not wait until the end of the day or the end of the week. Contemporaneous recording is a core principle of good laboratory notebook practices and is required for the notebook to be a legally credible document. For more on the standards that apply in regulated settings, see Lab Notebook and New Lab Setup Best Practices.

Key Takeaways

• A laboratory notebook is a bound, sequentially paginated, permanent record of your experimental work, written in real time in permanent ink.
• The four core principles are permanence, completeness, accuracy, and traceability; every entry must satisfy all four.
• Structure each entry with a header (date, title, objective), a detailed procedure, raw data, calculations, observations, and a conclusion with next steps.
• Record raw data directly in the notebook, never on loose paper, and clearly distinguish raw data from processed data.
• Correct errors with a single line through the original entry, followed by the correction, your initials, and the date; never erase or obscure.
• Attach loose materials such as gel images and printouts by taping them securely, labeling them, and cross-referencing them with the notebook page number.
• A notebook that records only successes is a falsified document; negative results are data and must be recorded.
• The notebook is a legal document that establishes priority of discovery and supports intellectual property claims; keep it secure, have it witnessed, and never remove it from the laboratory without permission.

Related Clinical & Scientific Guides

• MAPK Pathway: Mechanism, Function, and Clinical Relevance
• Mammalian Cell Culture Bioreactors: A Practical Guide
• Nucleotide Formation: Biosynthesis and Assembly of DNA/RNA Building Blocks