Yes - given what you've described (active follicles, mustache and chin/throat hair already coming in), your beard can absolutely still develop further. Here's what actually helps, in order of evidence strength:
1. Time - the biggest factor
Facial hair density typically keeps increasing until around age 25-30. At 22, with hair already actively growing in multiple zones, you are very likely still mid-progression rather than at your final density.
2. Fix the underlying driver - your celiac disease control
Since malabsorption from celiac disease can blunt the hormonal/nutritional signals that drive hair growth, staying strictly gluten-free and correcting any deficiencies (iron, zinc, vitamin D, B12) gives your follicles the best chance to respond normally. This is the single most relevant lever for you specifically, more than any product.
3. Topical minoxidil (evidence-backed, off-label)
- A 3% minoxidil solution applied twice daily has shown improved beard hair count and density in clinical studies, including a well-cited 2016 trial in men aged 20-60.
- Textbook pharmacology sources (Katzung's Basic and Clinical Pharmacology) describe its mechanism: it prematurely ends the telogen (resting) phase, prolongs anagen (growth) phase, and increases follicle size - though the exact molecular mechanism on hair follicles is still not fully understood.
- Effects take about 3-4 months to show, and initial shedding of existing fine hairs in the first month or two is a known, expected part of the process before regrowth.
- Effect is not permanent - stopping treatment reverses the gains over time.
- Side effects are usually mild (skin irritation/itching), but it's technically off-label for facial use, so worth discussing with a dermatologist first, especially given your existing health condition.
4. What generally does NOT work
Shaving frequency, "beard oils," biotin supplements (unless you're actually deficient), and testosterone boosters (risky and can suppress your own natural production) don't have solid evidence for increasing beard density in someone with normal-range hormones.
5. When to loop in a doctor
If growth stalls or you want to be thorough, ask for testosterone, LH/FSH, ferritin, zinc, and vitamin D levels, particularly since celiac disease can affect several of these. If levels are normal, minoxidil plus time is your most reasonable path; if something is deficient or low, correcting that will likely help hair growth more than any topical product.
Given you already have active growth, my honest read is this will keep filling in on its own over the next 1-3 years, and minoxidil is a reasonable option to speed that up if you're impatient, not something you strictly need.