Common Prescribing Errors – hints and tips for new FY1 doctors

Published: 7 May 2020 

Written by Laura Healey
(MPharm MRPharmS, PgDip Clin Pharm, PgDip Med Ed, FHEA)
Lead Pharmacist Education & Training, University Hospitals of Morecambe Bay NHS Foundation Trust
Clinical Tutor, School of Pharmacy and Biomedical Sciences, University of Central Lancashire

As a foundation doctor, prescribing the right medication can seem daunting. 21.3% of medication errors are related to prescribing, with prescribing the wrong drug or an unclear dose the most common problems (Connelly, 2019). The much quoted EQUIP study (2009) found 9% of junior doctor prescriptions contain an error. The study recommended prescribers receive feedback on errors to learn from their mistakes.

So which medicines are common areas of confusion?


Venous thromboembolism (VTE) and anticoagulants

VTE prophylaxis has been high on the agenda for many years now, complicated by the need for some patients to receive extended prophylaxis, e.g. patients with a total hip replacement. Low molecular weight heparins and the newer direct oral anticoagulants have different clinical indications and their use differs between organisations. The NICE NG89 guideline () is an excellent resource to support prescribing and has a number of additional tools and resources attached. Some key things to check before prescribing include renal function, platelets, patient weight and bleeding risk factors.

Warfarin is another story, as although dosing is based on INR, each patient may respond to the same dose change differently. the patient’s yellow anticoagulant book can give you an idea of previous responses, and the British Society for Haematology have some excellent guidelines for warfarin and anticoagulation (


Another common area of difficulty is analgesia, in particular opioids. The BNF’s analgesia section gives a handy summary of basic principles. The ‘prescribing in palliative care’ section contains a wealth of detail on dosing and safe use of opioids that can be applied to many situations, including dose equivalents between different types. this is particularly important when moving to a fentanyl patch. Always review renal and liver function when prescribing opioids as impairment can lead to accumulation, increasing adverse effects. Opioids are one of the most common medicines where you’ll encounter controlled drug prescribing legislation on discharge prescriptions. Some key things to include are the dose, frequency, route, dosage form and the total quantity to supply written in words and figures (for example Ten (10) tablets). Do think carefully about quantities you are supplying. I have encountered the occasional prescription for several months’ worth of opioids as the prescriber had not quite realised their mistake! Again, the BNF has a handy ‘controlled drugs and dependence’ section to refer to if you are not sure.


In the last few years there has been a huge expansion in the insulin market. Understanding which insulin type the patient is prescribed, and in which formulation (pen, cartridge, innolet etc), is essential. Also, there are now biosimilar insulins, so it must always be prescribed by brand to avoid confusion as they are not dose equivalent. Not all insulins come as 100units/mL, there are now many at 200 and 300 units/mL, so pay careful attention to details on strength. The Joint British Diabetes Society has a wide range of guidelines available for different clinical situations, including insulin infusions (

Nil by Mouth (NBM), enteral feeding tubes and dysphagia


These pose unique challenges for medicine administration. Firstly, you need to know if changes to a feeding route are temporary or permanent and which route(s) of access for medicines administration you have available. Next, consider rationalising which medicines are essential. Then use the BNF to determine   if there are dispersible, liquid or injectable formulations available for these drugs. However, more specialist resources may be needed, and this is where your pharmacist will be ideally placed to offer support. You may also need to wait for a speech and language therapist (SALT) assessment before proceeding. Just because something is a liquid does not mean it is suitable for a feeding tube, and you may find yourself switching to completely different medicines for the patient. Manipulation of oral formulations is commonplace, but always remember this is outside the terms of the drug’s licence and not possible for all formulations.

Intravenous fluids

Another common prescribing query! The NICE guidelines ( has a good deal of content and supporting resources.  E-learning for healthcare ( also has an intravenous fluid therapy module you can work your way through.

Drug interactions

You will never remember all drug interactions as there are too many and they are constantly updated. The BNF app has a useful interactions checker, although some clinical interpretation might be needed. For example, you know using two antihypertensives together will cause hypotension as that was the intended outcome!

The cytochrome P450 enzyme inducers and inhibitors are good to know, in particular the ones in your area of practice. Even if you can’t remember the details just knowing they affect the CYP system makes you think twice before prescribing. Other interactions to look out for are dietary and herbal products. Many patients purchase over the counter preparations that can interfere with prescribed medicines, conditions or interventions. For example, glucosamine, popular for joint conditions, can affect INR whilst on warfarin, and ginkgo biloba and garlic affect clotting.

So how can you prevent prescribing errors?


Unfortunately, you cannot wholly eradicate them, however, here are some useful resources that might help promote safer prescribing:

  • British National Formulary (BNF) app – the online version is free to access, updated regularly and much easier to find than a paper version! Make sure you are in the right version as you can toggle between the adult and children’s version in the same app. Some of you might also have access to the Medicines Complete app as well, through which you can access the BNF.
  • Pharmacy – Find out how to get in contact with the pharmacy department; you may have a ward pharmacist you can speak to in person. Some hospitals have a medicines information department that will field queries.
  • Electronic Medicines Compendium ( – This provides monographs (SPC) for most medicines and expands on the data found in the BNF if you want more information on for example its pharmacokinetic properties, side-effects, compatible diluents etc.
  • MHRA Drug Safety Updates ( – These are monthly bulletins which contain the latest advice and warnings for prescribing and are free to sign up to.
  • Local prescribing policies, guidelines and systems – each organisation will have their own, especially for antibiotics. Make sure you find out how to locate them and look at the common ones you will be using in each rotation. You may be prescribing by hand, electronically, or a mixture of the two. Again, it is essential you know what is expected of you and how to use it as this sets the groundwork for safe prescribing.

My advice to you would be:

  • take your time (I know it’s much easier said than done!)
  • think carefully
  • use the resources available to you
  • always know your limits
  • don’t be afraid to ask for help

The key phrase you will hear me uttering to any trainee or student is “there is never a stupid question” as it is always better to ask than try and muddle through and potentially leave yourself open to error. Good luck!


Connelly, D. (2019) Medication errors: where do they happen. Pharmaceutical Journal, 22nd Feb 2019: 302 (7922). Available online: Dornan T et. al (2009) EQUIP study. General Medical Council. Available at: [Accessed 30/04/2020]

Scroll to Top


Elliot is a St George’s graduate currently working as an F1 Doctor in East London. As the first in his family to apply to university, Elliot is well aware of the barriers that can be faced in trying to get to medical school. He is passionate about widening access to medicine for underrepresented groups.
 He was the representative for St George’s on the BMA Medical Students Committee, and has done lots of work with local schools and colleges to raise awareness of medicine as a career, as well as working on admissions policies with the widening participation team St George’s. Elliot is part of the @BecomingaDr outreach team and National Health Careers Conference Team.