Terri McCue, from the south side, is taking legal action because she says Andrew, 19, who has Down's syndrome, is not being assessed in the right way.
After filling out the self evaluation questionnaire (SEQ) with a social worker, the mother-of-two was offered £9500 a year to pay for Andrew's support needs. She queried the outcome and was allocated £10,300.
However, Ms McCue says Andrew needs around £17,000, which would pay for his care. The 56-year-old grandmother-of-one said: "In one of the SEQ questions, the council said Andrew needed help once a week. But he needs help every day. If it's once a week then I'm asking them what day is it he needs help? Is it a Monday? Or a Saturday? It's just a tick box exercise and they are not taking into account Andrew as a person."
The first hearing is due at the Court of Session in Edinburgh on May 9.
The council says that self-directed support is designed to give families and individuals choice. It is part of personalisation, a policy being rolled out nationally.
Susan Aitken, SNP councillor for Langside, said: "It is no surprise that, sooner or later, a family was going to feel forced to take legal action."
Helen McCourt, 49, from the East End, said the budget of around £8500 that was allocated for her daughter, Laura, 31, who has Down's syndrome, would drive her "deep into poverty". She said: "We would end up having to go to a food bank."
However, Kim Kenny, 49, said the system was effective now for her 22-year-old son Jamie, who has autism. She said: "It is working for him at the moment but I am fearful of what will happen when Jamie is older."
A council spokesman said: "We are always willing to listen to those with a stake in the system and will make improvements where necess-ary. However, we are fully confident the personalisation system is being operated appropriately."