Many employers do not understand the terrible effects of migraines and could do more to support staff with the condition, three UK charities say.
With one in seven people affected, their research suggests more help and awareness from bosses is needed.
Fiona McKenzie, 33, was told by one of her former employers she would be fired if her absences due to migraines didn't improve.
She says migraine pain is "like someone hitting my brain with an ice pick".
In a survey of more than 2,000 UK adults by the Migraine Trust, Migraine Action and the National Migraine Centre, 64% said they thought employers were not properly informed about the nature of migraines or how they affected employees.
One in five believed health professionals were not fully aware of the impact of migraine on their patients either.
Nine million people in the UK are thought to have them, with women more likely to be affected than men.
The most common migraine symptoms are:
- throbbing headache
- sensitivity to light or noise
- nausea, feeling sick
- seeing flashing lights or coloured spots
- double vision
Fiona, who lives in London, says she has some of her worst migraines at work.
At their worst, they affect her vision, cause a stabbing pain in her head and leave her unable to talk. She also becomes sensitive to loud noises, light and smells.
Although she has had some very understanding managers, she says she has also experienced a complete lack of support.
"[Some time] ago, I had 16 headache days in one month, and it had a real impact on my work, although I tried hard not to take sick days."
But her employer simply told her to pull her socks up and be more resilient.
Fiona says: "I found it very hard, it pushed the onus on to me, but it was not something in my control.
"It feels like you're fighting an illness all by yourself.
"I came home and cried on the sofa because I couldn't magically make myself better."
'Excuse for a sickie'
Although migraine can be classed as a disability if it is severe enough to affect work, charities says the legislation is unclear and many employers are reluctant to act.
Every year, an estimated 25 million days are lost because of migraines in the workplace and in schools in the UK.
Simon Evans, from Migraine Action, said most people with migraines "kill themselves to get in to work".
He said employers should consider how lighting and computer screens could affect staff with the condition, and offer a sick room that is dark and quiet where people could go to recover. They should also send home those affected, if necessary.
"No two migraines are the same. People feel they can't say they are suffering because it's often used as an excuse for a sickie."
Fiona says she would like employers to be more sympathetic, offer flexible working and encourage staff to seek help and treatment.
She had to push to see a neurologist because her GP was sceptical that anything more could be done to relieve her migraines.
Yet there are a variety of treatments and preventative medicines available, depending on how regular and how serious the migraines are.
If you are having four or more migraine attacks per month, the advice is to discuss how to prevent attacks occurring with your GP - rather than taking painkillers once they start.
New research, published in the journal Headache, found that measuring daily stress levels could help predict when migraine attacks were going to occur in those who got them frequently.
Arlene Wilkie, chief executive at The Migraine Trust, said charities were able to provide everyday support for migraine sufferers and campaign for more support in the workplace.