Purpose To investigate the incidence of transcription errors in a busy main teaching hospital in Pakistan and to test the impact of medication’s name lettering, dose expression styles and nurse’s duty duration on the incidence of transcription errors. Methods Inpatient medication chart (n=1000), discharge patient medication chart (n=1000), and dispensed items sheet (n=1000) transcripts were reviewed for transcription errors by a risk management panel composed of two physicians and two pharmacists. Panel members screened scans independently and a risk manager arbitrated disputed ratings. Transcription errors were classified according to their severity into 6 categories: A1, A2, B, C, D, and E. Orthographically similar medications (n=20) were handwritten in lowercase and Tall Man approaches on identical charts; similarly, decimal doses were expressed uncovered and covered, and metric doses were expressed with and without trailing zero. To investigate the impact of writing style and long duty hours on the incidence of transcription errors, nurses (n=25) were recruited, anonym charts were placed into envelops and were administered on nurses in a double-blind randomized crossover design at 1, 6 and 10 hours after the commencement of the nurses’ duty. Results During the study, nurses transcribed 6,583, and 5,329 medications from medication charts and discharge medication sheets, respectively. Similarly, dispensers labeled 6,734 dispensed items. Of these, there were 1,112, 737, and 411 transcription errors, giving an error rates of 16.9% (95% CI: 13.8-19.1), 13.8% (95% CI: 11.2-15), and 6.1% (95% CI: 5.4-7.8), respectively. Of all errors 81.3% were minor errors (ratings A-B), while the rest of errors 18.7% were classified serious errors (ratings C-E). Transcription errors were statistically significant (p<0.001) at 10 hours after the commencement of the duty. Tall Man lettering approach, covered decimal points and avoiding trailing zeros with decimal units significantly reduced transcription errors (p<0.001). Conclusion Transcription errors increase with increasing duty hours. Differentiating orthographically similar medications and the use of proper decimal and metric units reduced transcription errors.