This is a question which most of us have wrestled with at one time or another; in truth, the issues are far from black and white and the way forward might look different for various people. This notwithstanding, we can certainly find helpful guiding principles in Scripture.
Homelessness and begging exist for all sorts of reasons. I am reminded of Jesus' words, 'The poor you will always have with you.'  Behind every individual is a story. We may not always have time to explore people's stories, but when you can and if it's safe to do so, try to start a conversation. Begin by introducing yourself and finding out their name, then ask a question like 'How long have you been on the streets?' or, 'What's your story? 'It's not wrong to show a degree of discernment about giving. In East London where I live, I can think of at least one individual who has for years been recounting the same story of needing to buy a train ticket to visit a sick relative at very short notice. If the long-standing nature of the crisis is pointed out, he becomes very angry. This said, there is nothing wrong with a bit of naivety — better to be naively generous than cynically tight-fisted. Love always hopes. 
Sometimes the offence we might feel at having been 'taken for a mug' has more to do with injured pride than concern over the person's possible drug or alcohol use. I don't know about you, but my pride needs all the knocks it can get.
Sadly, despite the UK's relatively well-developed benefits system and charitable sector, and looking beyond those 'just seeking the next fix', there is no denying that we do have an abundance of poverty on our streets. We can close our eyes to this, or we can let the reality of it touch us.
God's word is full of injunctions to look after the poor, the oppressed, and the downtrodden.  This refers not only to practical help, but also to affording them dignity and value.
In some instances, it will be right to give; more difficult in a cashless society. Some might decide before the Lord always to carry, for example, a £2 coin, so this is available when needed. Others might have a rule not to give cash but to always offer to buy a sandwich or meal deal.
Be aware of local services to signpost people to when appropriate — for food and night shelter, or GP outreach services, Covid vaccination and testing facilities, and needle exchange programs.
You may be able to volunteer, and for some the Lord may particularly lay this issue on your heart. Explore local opportunities, for example, in a night shelter or soup kitchen, or raise money for a homeless charity. One friend does a sponsored 'sleeping rough' each year.
In everything, check your heart. Watch out for a hardened heart or a mean attitude masquerading as 'clear-sightedness'.
If you have a burning question, email us at: email@example.com. The best question each issue wins free student membership for a year.Abigail Randall, a GP in East London and medical school link for Bart's and the London Medical School