Prescribing basics

Prescribing Basics

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Prescribing is an important component of patient care, which unfortunately can very easily go awry. The dangerous nature of prescription medications means that the process of prescribing is heavy regulated through legislation, clinical guidelines, local, regional and national protocols. What may seem like a relatively simple and straightforward process can sometimes be much more complex than it first appears.

Prescriptions represent a request from one healthcare professional to another to administer or supply medication to or for a patient. Some medications do not require a prescription as they are considered safe enough for patients to use without professional supervision and these are legally classified as general sale list medications (GSL). Medications that are considered less safe and require supervision by healthcare professionals are classified as prescription only medications, referred to as POMs and can only be used under the supervision of a prescribing healthcare professional. Anything that is not a GSL or POM is classified as a pharmacy medication or P medicine, which is only available under the supervision of a pharmacist.

Something you should consider first is the practical elements of prescribing. Prescribing can be completed in a range of formats, from the technical methods that use ePrescribing systems or β€˜regimen prescribing’ (where users click a button and automatically prescribe a combination of medications) to handwritten prescription using pen and paper, or a combination of both.

The technical aspects of the prescription will vary from place to place but there a few key elements of the prescription that will remain the same, as these are required by law in the United Kingdom (namely the Medicines Act 1968, Misuse of Drugs Act 1971 and Pharmacy Order 2010). This is particularly true for products that are likely to be misused and require extra controls to manage their supply. These products are known as controlled drugs and are grouped into schedules, from 1-5, where 1 indicates a high likelihood for abuse with little clinical application and 5 indicates a clear clinical application with a low likelihood for abuse. This differs from the class system used by Her Majesty’s Courts and Tribunals Service to categorise criminal possession of substances.

You might also be interested in our prescribing safety assessment (PSA) question pack, which contains over 500 high-quality PSA questions. We also have a range of prescribing stations in our collection of 1,300 ready-made OSCE StationsΒ πŸ’Š

The patient

Any prescription must include the patient’s name. This information is used to identify the patient and ensure that the right medication is given to the right patient. The address of the patient could be their residential address, care home or the ward the patient is on. The age or date of birth of the patient is a useful way to identify the patient, however for patients under the age of 12 years it is a legal requirement to include the age or date of birth. Age is a useful indicator of liver and kidney function as well as fat/water ratio which can alter the distribution, metabolism and elimination of medication from the body. This makes the age of the patient an essential piece of information when deciding if medication is clinically suitable. This is particularly important for children, hence the legal requirement, but also for elderly frail patients so including the age or date of birth of the patient represents good clinical practice.


  • Full name
  • Address
  • Age or date of birth (must be included if the patient is under 12 years old)

The medication

Just like the technical aspects of prescribing, what can be prescribed will depend on where you are working and your level of training. Some medications can only be prescribed by healthcare professionals that are authorised to do so. This is typically the case for very expensive medications or very dangerous medications, such as chemotherapy or intravenous immunoglobulin.

You should check that you are authorised to prescribe the medication(s) you are trying to prescribe. This can be done easily on electronic systems, as the system may only let you select items you are authorised to prescribe, however, if using a manual prescribing process you should check the following resources:

  • Clinical supervisor
  • Practice or trust formulary
  • Local formulary – developed by local and regional drug and therapeutics committees and usually available online
  • Nurse Prescribers’ Formulary – for community nurse prescribers, available online
  • Dental Practitioners’ Formulary – for dentists, available online

Decisions about which medication should be prescribed should be shared with patients and carers. About 1 out of every 10 prescribed medications are never started and about 50% of medications are not taken as they’re prescribed. Including patients in decisions about their care increases the likelihood that they will start and continue to take their medication.

Information that should be included on a prescription

Name of the drug

It is best practice to use the β€˜generic’ or the actual name of the drug, rather than a branded product name, for most medications. As this will be cheaper for pharmacies to supply.

However, some medications should be prescribed using their branded name, particularly if they have a narrow therapeutic range. This means that the metabolism, distribution and elimination may be different between formulations of the same drug. For example, Lithium should be prescribed using the branded names of Priadel, Camcolit and Liskonum to ensure consistent drug serum levels.

The name of the drug must be included for schedule 2 and 3 controlled drug prescriptions.


This is the β€˜form’ you would like the medication to be in and describes how the drug will get into the patient. For example, as tablets, capsules, solution, elixir, suppository, pessary, cream, powder, pressurised inhaler, dry powder inhaler, subcutaneous injection, intramuscular injection or infusion.

There are many formulations available for most medications and if you’re unsure about which formulation to prescribe you should make a shared decision with the patient, if possible. If you’re not sure what form the medication takes, try and contact a pharmacist or pharmacy technician, who should be able to find out for you.

The formulation must be included for schedule 2 and 3 controlled drug prescriptions.


This is not the dose! The strength relates to how much drug is in the formulation you have requested. For example, 10mg tablets or 5mg tablets.

The strength must be included for schedule 2 and 3 controlled drug prescriptions.

Dose or instructions

Historically, doses were written using Latin and over time these were abbreviated. For example, omni die or once a day is abbreviated to OD. Many errors relating to prescriptions are caused by folks not just failing to read Latin, but failing to read abbreviated Latin! For example, quatro die or four times a day is abbreviated to QD, which can be misread as OD, if handwritten, leading to sub-therapeutic doses. To avoid errors then, try to write doses using plain English such as once, twice, three times (avoid thrice) or four times per day.

Doses can be β€˜licensed’ or β€˜unlicensed’. Licensed doses have been approved by regulators who have assessed the evidence for the product at a particular dose for a particular reason (or indication). Unlicensed doses or β€˜off licence’ doses have not been approved and the evidence for use of the medication at that dose for that indication has not been assessed. When prescribing β€˜off licence’ responsibility for the safety of the products use rests solely with the prescriber.

The dose of the medication should be checked in reliable resources, such as an up to date copy of the British National Formulary.

Some medications require a loading dose to enable a therapeutic serum level to be established quickly. For example, Warfarin requires the patient to be β€˜loaded’ with a short term high dose followed by a longer-term lower dose. If you’re unsure if a medication requires a loading dose, contact a pharmacist.

Additionally, some medications have narrow therapeutic ranges, this means that patients can quite quickly build up toxic levels of the drug in their body and professionals need to monitor this. A very common example of this would be the Vitamin K antagonist Warfarin, which we monitor using the International Normalised Ratio or INR for short. The therapeutic range of a medication often depends on the indication and the patient, so make sure to check or set these for each prescription individually. Other approaches to monitoring may focus on the patient’s response to medication, for example monitoring white cell counts with clozapine, liver enzymes with statins or renal function with angiotensin-converting enzyme inhibitors.

Antagonists that block receptors should be introduced at low doses and gradually increased and, when stopping treatment, should typically be withdrawn slowly.

Dose or instructions must be included for schedule 2 and 3 controlled drug prescriptions.


Quantity should be used to describe how long you would like the patient to use this medication. Many different units of measure can be used (e.g. days, weeks, months) or the actual quantity of medication you would like to be supplied (e.g. 7 tablets).

For schedule 2 or 3 controlled drugs you must include the actual quantity of medication you would like supplied in words and figures (e.g. SEVEN (7) tablets).


To summarise, good prescribers include the following information:

  • Name
  • Form
  • Strength
  • Dose
  • Quantity
Table 1: Common controlled drugs used in practiceΒ  Schedule
Morphine Schedule 2
Codeine Schedule 5
Tramadol Schedule 3
Pregabalin Schedule 3
Temazepam Schedule 3
Fentanyl Schedule 2
Oxycodone Schedule 2
Zopiclone Schedule 4 Part 1
Somatropin Schedule 4 Part 2
Cannabis Schedule 1

The professional

Many times as a junior prescriber you may be asked to sign a prescription, however, not every healthcare professional has the authority to prescribe every medication. For example, junior doctors can not prescribe chemotherapy. During the signing of the prescription, it is important that enough information is provided to create a record of which healthcare professional is authorising the supply or administration of a medication. This enables prescribing practices to be audited and ensure that poor practices are identified.

Information about the prescriber that is required by the person signing the prescription is discussed below.


This should be legible and be your β€˜professional name’.

Authority to prescribe

This should indicate what qualification the professional has to prescribe. For example, an MBBS degree, a BDS degree or an independent prescribing qualification, membership of an association or accreditation. This could also include a particular role within an organisation.

This could also be a registration number with statutory bodies that can be checked to verify a prescribers status, such as the GMC, GPhC, GDC and NMC.


This should include the date that the prescription was issued by the professional. This may be different from the date that the prescription should be started and if the prescription is to begin on a specified date this information should be included under the dose or instruction section of the prescription.

Prescriptions can be pre-dated (for a time in the future) but should not usually be post-dated (to cover a period of use in the past) unless there are exceptional circumstances. For example, pharmacists can make supplies of medication legally if there is an agreement for a prescription to be written within the next 24 hours.

What you need to decide: patient safety

The therapeutic decision-making process is influenced by lots of different things. Primarily, all therapeutic decisions should involve the patient and their carers, if possible.

All medication comes with side effects and avoidable adverse drug reactions cost the NHS approximately Β£98.5 million per year. Whenever you’re prescribing medication, you should always consider the risk and benefits of the medication. A good way to do this is to consider the necessity of the medication.


Once necessity has been identified, you should consider how much of the medication is needed for a therapeutic effect. This decision should be evidence-based but person-centred. For example, some randomised controlled trials will identify a therapeutic dose, however, the participants in the trial may be very different to the patient in front of you.

Most medications are prescribed according to actual body weight (mg/Kg) but beware of hydrophilic medications that require dosing via ideal body weight, such as gentamicin.

Watch out for daily versus divided dosing (e.g. Paracetamol 15mg/Kg/dose or 60mg/kg/day).

Prescribing too much medication can lead to dose-dependent side effects, wastage and inappropriate polypharmacy so try to use the smallest dose for the shortest period where possible.


After dosing, consider the duration. Does the medication require acute or chronic use? Is this acceptable to the patient?

This is a particularly useful consideration for treatments that can cause dependence such as opioids, benzodiazepines, z-drugs, gabapentinoids as well medication where long-term use can lead to complications (e.g. corticosteroids) or resistance (e.g. antimicrobials).


Before finalising a prescription, you should dedicate some time to reviewing what other medication the patient takes (if any) and how this newly prescription may interfere with absorption, distribution, metabolism and elimination of other medication. This can be tricky as interactions can be significant or non-significant. Useful resources include Stockley’s Drug Interactions, the BNF, MedicinesComplete Interaction Checker and a pharmacist or pharmacy technician.


The therapeutic effect of medication requires monitoring. This may include regular reviews with the patient regarding their symptoms as well as ordering and reviewing tests such as full blood count, liver and kidney function tests, eye tests, and lung function tests.

When making a plan to monitor medication, always consider and identify who will do this and by when. Pharmacists can help in monitoring long-term conditions and therapeutic outcomes, including making recommendations to deprescribe medications which are no longer beneficial for the patient.

Table 2: Medications with a narrow therapeutic range

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