Migraine prevention injections — what CGRP treatment involves
Quick answer
Migraine prevention treatment reduces how often attacks happen, rather than treating pain once it has started. Options usually begin with daily tablets such as propranolol, topiramate or amitriptyline. CGRP injections like Emgality are typically considered after several standard preventive medicines haven't helped or weren't suitable. A clinician can assess which approach fits your pattern of migraine.
What counts as migraine prevention treatment?
Migraine treatment falls into two categories. Acute treatment — painkillers, anti-sickness medicine or triptans — is taken during an attack to ease symptoms already underway. Prevention treatment is taken regularly, whether or not you currently have a headache, with the aim of reducing how often attacks happen and how severe they are.
Prevention is usually considered when migraine is frequent enough to affect daily life — commonly defined as four or more migraine days a month — or when attacks are so severe or disabling that acute treatment alone isn't managing things well. It's also worth thinking about prevention if you find yourself relying on acute painkillers or triptans several days a week, since using these too often can itself contribute to more frequent headaches.
Migraine is usually described as either episodic (fewer than 15 headache days a month) or chronic (15 or more headache days a month, with at least 8 having migraine features). This distinction matters because it affects which preventive options are considered appropriate and how treatment is monitored over time.
Standard first-line preventive tablets
For most people, prevention starts with a daily tablet. The three most commonly used first-line options are propranolol, topiramate and amitriptyline. Which one a clinician suggests depends on your overall health, any other conditions you have, and what else you may already be taking.
Propranolol is a beta-blocker and isn't suitable for everyone, including some people with asthma or certain heart rhythm conditions. Topiramate can affect mood and concentration, and isn't used in pregnancy or in anyone who could become pregnant unless additional precautions are in place, because of the risk it poses to a developing baby. Amitriptyline is taken at a much lower dose for migraine than for its original use as an antidepressant, and can cause drowsiness, particularly when starting out, so it's often taken in the evening.
A trial of a first-line tablet is usually given several weeks to show whether it's helping before switching or adjusting the dose — migraine prevention tends to work gradually rather than immediately, and doses are often increased slowly to reduce side effects. If a first tablet doesn't suit you or doesn't help enough, it's common to try a second or third option from this group before moving on to other approaches.
When are CGRP injections considered?
CGRP injections such as Emgality aren't usually a first step. They're generally considered for adults who have tried at least three other preventive medicines that haven't worked, weren't tolerated, or weren't suitable because of other health conditions, and who continue to have at least four migraine days a month.
This staged approach reflects how these medicines are funded and prescribed in the UK — they're reserved for migraine that hasn't responded to more established, lower-cost options first, rather than being an early-line choice. In practice, this means keeping a record of which preventive tablets you've tried, at what doses, for how long, and why they were stopped, since this history is usually needed to assess eligibility.
Because everyone's migraine pattern and treatment history is different, eligibility is always assessed individually rather than applied as a blanket rule, and a clinician will want to understand how migraine is currently affecting your day-to-day life before recommending next steps.
How CGRP treatment works
CGRP stands for calcitonin gene-related peptide, a protein involved in transmitting pain signals during a migraine attack. CGRP injections are monoclonal antibodies that work by blocking this protein or the receptor it acts on, which can reduce how often migraine attacks occur. This is a different mechanism to older preventive tablets, which weren't originally developed for migraine and act more broadly on the nervous system.
Emgality is given as a monthly injection using a pre-filled pen, and is designed to be self-administered at home in the same way many people already manage other injectable treatments — under the skin of the abdomen, thigh or upper arm. Training on the injection technique is usually given before starting, and most people find it straightforward to fit into a monthly routine once they're used to it.
What to expect from a course of treatment
Treatment is usually reviewed after around 12 weeks. As a general guide, continuing beyond this point is typically supported if migraine days have reduced by at least half for people with episodic migraine, or by around a third for people with chronic migraine. If there's little or no improvement by this point, a clinician may suggest stopping or trying a different approach, since these medicines don't work for everyone.
The most commonly reported side effects are reactions at the injection site, such as redness, swelling or itching, along with occasional constipation. Most people tolerate treatment well, but any new or troubling symptoms should be discussed with a clinician. Regular review appointments are used to check how well treatment is working, monitor for side effects, and confirm it's still the right option as time goes on.
Botulinum toxin as an alternative for chronic migraine
For chronic migraine specifically (15 or more headache days a month, at least 8 of which are migrainous), botulinum toxin type A injections are another option recognised for use once several standard preventive medicines haven't helped. This is given as a series of small injections across the head and neck by a trained clinician, usually repeated roughly every 12 weeks. It isn't used for less frequent, episodic migraine, and — like CGRP injections — is generally only considered after other preventive tablets have been tried without enough benefit.
Some people are suitable for either botulinum toxin or a CGRP injection, and the choice often comes down to personal preference, how the appointments fit around your routine, and clinical judgement about what's likely to suit you best.
Lifestyle support alongside prevention treatment
Whichever preventive approach is used, everyday habits still matter. Keeping a simple diary of when attacks happen can help identify personal triggers, such as skipped meals, dehydration, poor sleep, or stress, and can also be useful evidence when discussing treatment options with a clinician. Regular sleep and meal times, staying hydrated, and moderating caffeine can all support fewer attacks for some people, even if they don't remove the need for medical treatment.
It's also worth being aware of medication overuse headache, which can develop when acute painkillers or triptans are used too frequently and can end up making headaches more frequent overall. As a general guide, using acute treatments on 10 or more days a month over a sustained period is a common trigger for this. A clinician can advise on safe limits for acute medicine use alongside any preventive treatment, and on how to approach cutting back if overuse has become a factor.
Getting started with a consultation
If migraine is affecting your daily life and standard tablets haven't helped, a consultation is a starting point to review what you've already tried, discuss whether CGRP treatment or another option may be suitable, and agree a plan for follow-up. Bringing details of previous preventive medicines — what you tried, the dose, how long you took it for, and why it stopped — will help a clinician assess your options more efficiently.
Frequently asked questions
How is migraine prevention different from treating an attack?
Acute treatment is taken during an attack to ease pain and other symptoms. Prevention treatment is taken regularly, regardless of whether you currently have a headache, with the aim of reducing how often attacks happen over time.
How many migraine days a month would mean prevention is worth considering?
Prevention is often considered from around four or more migraine days a month, or when attacks are frequent or severe enough to significantly affect daily life, though this is assessed individually.
Is Emgality available on the NHS?
Emgality (galcanezumab) can be prescribed on the NHS for eligible adults who meet specific criteria, including having tried and not responded to several other preventive medicines. Suitability is assessed on an individual basis.
What side effects can CGRP injections cause?
The most commonly reported side effects are reactions at the injection site, such as redness or itching, and occasional constipation. Most people tolerate treatment well, but you should discuss any new symptoms with a clinician.
How soon will I know if prevention treatment is working?
Treatment is typically reviewed after around 12 weeks to assess whether migraine frequency has meaningfully reduced. It can take a few months to see the full effect, so short-term fluctuations aren't unusual.