It would go something like this: "I don't think I can help you, let me suggest a ____________ to help you with your situation."
"This is outside the scope of my studies and experience. Can I refer you to a ________________."
Entry level cojones are required to hear those words come from your mouth and to not waste your client's time.
If I suspect your body is ravaged by inflammation, I will not pray away your inflammation with you. I have the sense to ask if you had blood work done and are you treating that with your doctor. I may even ask for insight: "If I may ask, how are you and your doctor approaching it?"
[See how I just got some free education in that interaction? They paid for a doctor visit, and I asked them about an educated interaction--this gives me resources for further study.]
I will not "heal" your low testosterone levels--I'll suggest you work with a nutritionist or some such professional--I won't perform a testosterone ceremony for the raising of all your T-levels. Good grief.
Know your limits.
Professionals need help too.
Now it gets personal.
There are those that will expend the energy to refuse good help. "Take the help;" a teacher of mine famously punctuates her workshop introductions with this. That may mean, take the good-heartedness of the interaction, take the lovingness, take the well-meaning intent and make use out of it--practice recognizing, opening up to, and receiving the good. It would be a shame for good hands, good intent to go to "waste" on someone fortifying their reluctance.
In fact, from the giving side of it, I can say, it feels downright crappy. When a receiver "shows you the hand," I feel saddened.
"Really," I want to say, "I cannot help you? ...at all?"
"Truly? There's nothing here that can be beneficial?"
I'm sure I'll be remarking a lot more on giving/receiving...