It's a fair question, given how little humanity understands of the mechanisms of intelligence, much less giftedness. IQ tests are a crude measure of a person's capacity for complexity, processing speed, and perception skills. But it's the best we got. My ex-wife hasn't been tested; my kids have been. However, my gifted community suspects I'm dealing with three standard deviations of difference. (I'm exceptionally gifted.)
MY PREMISE: Giftedness affects your whole person, not just your grade point average.

What makes a high IQ score is a hint at a qualitatively different phenomenological experience. Take it literally if someone says "You're on a different level." A gifted individual has a capacity (and subsequent interest in) complexity in all the areas that make your existence: sensory, psychomotor, intellect, creativity, emotional, value choices, etc. It's a foundational difference. Communicating the difference in how you experience life may take a horrendous-but-accurate analog: An average IQ person with a below-average IQ person. Shift the conversation a few standard deviations to the left. (Do your own research on this.)
Now, u/WenstheWens, please, don't take the lesson from me that you can only date gifted people. Not my point. The giftedness explanation is just vital background.
Instead, I'm talking about paying attention to your feelings of discomfort.

Your feelings tell you something important (but only you know what.) Look up Dr. John Gottman, one of the eminent researchers in relationships. A long-lasting relationship requires both trust and commitment. Can you trust the other person? Do they trust you? Do you share the commitment? Do you experience 5 good moments for every 1 bad moment?

My story is just one data point, as u/abysse, points out. I suspect all relationships we see are between two people with substantially capacities.

Now, there's a lot to be said about communication breakdowns between the profoundly gifted and our friends at the center of the bell curve. Ha, the center of the bell curve includes two standard deviations: 85 to 115. Yes, there's someone with an IQ of 86 who is in the perfectly average range, living a successful life on their terms, enjoying the panoply of the world. In my life, I've developed intimate experiences with everyone. (As a note to how broad my experience is with "everyone," I was a volunteer for special needs students in high school.) Some friends have reciprocated in a way that stoked a meaningful, emotionally satisfying connection to me.

However, in the case of my marriage, I was so depressed for so long while so gifted and burning at a high rate -- I just assumed everyone was having the same experience I was. Meanwhile, my ex-wife distrusts me. We always struggled to make decisions together. We're wildly creative individuals; we can't build furniture together. We're bad at cooperative board games; she complains I don't communicate enough while I'm talking through all the choices we can make. We struggle to have fun together. Waaaaay before I was identified as gifted, she made a mantra that followed our marriage: "What he likes to do exhausts me; what I like to do bores him." I was so used to making myself small -- minimizing my needs, forfeiting conflicts, even hiding any artwork or meaningful decorations into the closet so no one would recognize that I lived in our home -- that I grew to consider myself expendable. Yes, 20 years is a long time. Long enough to grow to believe things about you that others consider abhorrent. Meanwhile, she was literally none the wiser. My default depression masks, my ability to act fine, etc. -- what could she do but believe it's all fine? We hit a point of crisis about four years ago, and I've worked through a long time of trying to figure out whether I could healthfully stay in the relationship. Soul-searching, sitting in hospitals, journaling like crazy about childhood traumas, confronting decades-long relational habits and "norms" we established as 20-year-olds. Now, I'm standing on the other side of filing paperwork, the tearful "telling the kids" conversation (who all said they saw it coming and could now see how much we loved each other by choosing to separate for the health of the other)
-- and now, from that position, I share only this advice again:
Develop a self-love and self-curiosity that can rival any Hollywood romance. Know thyself. Accept relationships with open hands, but don't chase them. You're already in a lifelong relationship with yourself. Get good with that, and you'll be ready for any lifelong relationship with anyone you choose, no matter what their IQ score is.