LL-37 Dosing: 5 Mistakes I Made (So You Don't Have To)

I wasted probably $800 on LL-37 before I figured out what I was doing wrong. It was 2021, I'd just had success with BPC-157 for some lingering shoulder issues, and I kept reading about this "master antimicrobial peptide" that could supposedly boost immune function and help with gut issues. I was dealing with recurring sinus infections every few months, so I thought, why not? Turns out there's a massive difference between buying a peptide and actually using it correctly. Let me save you the time, money, and frustration I went through.

Quick Answer: The most common LL-37 dosing mistakes are starting too high (should be 200-500mcg daily), not timing injections correctly (empty stomach essential), poor reconstitution technique (ruins peptide structure), inadequate storage (degrades fast at room temp), and not cycling properly (continuous use reduces effectiveness). LL-37 is the only human cathelicidin antimicrobial peptide—a 37-amino acid cationic peptide that fights bacteria, viruses, and fungi.

What Actually Is LL-37? (The 60-Second Science)

LL-37 is the active form of hCAP18, your body's natural antimicrobial peptide. Think of it as your immune system's Swiss Army knife—it punches holes in bacterial cell membranes, disrupts viral envelopes, and even helps regulate inflammation. Your body makes it naturally, but production drops with age, stress, and certain health conditions.

I'm not a medical professional, just a guy who reads way too many research papers at 11 PM. But after spending probably 40+ hours researching this stuff when I first started, here's what matters: LL-37 is a cationic (positively charged) peptide, which is why it's attracted to negatively charged bacterial membranes. It's got broad-spectrum activity against gram-positive bacteria, gram-negative bacteria, fungi, and even some viruses.

The cool part? It does more than just kill pathogens. It modulates your immune response, promotes wound healing, and may even help with gut barrier function. That's why I was interested—I wasn't just fighting infections, I was trying to fix the underlying immune dysfunction.

Mistake #1: Starting With Too High a Dose

This was my first screw-up, and it's apparently super common. I read one forum post about a guy using 2mg daily and thought, "More is better, right?" Wrong. So wrong.

I started at 1mg (1000mcg) daily, subcutaneous injection in my abdomen. Within three days, I had the worst acne breakout I'd experienced since high school. My face looked like a pepperoni pizza. Turns out, LL-37 stimulates sebum production and can trigger inflammatory responses when you dose too aggressively.

What I should have done: Start at 200-300mcg daily and assess tolerance for at least two weeks. Most people respond well to 300-500mcg daily. The research I found later suggested that therapeutic benefits appear at surprisingly low doses—you're working with nanogram-to-microgram concentrations at the cellular level.

When I dropped down to 300mcg daily, the acne cleared up within a week, and I actually started noticing the benefits I was looking for—fewer sinus issues, better recovery from workouts, and generally feeling less run-down.

Mistake #2: Ignoring Injection Timing

For the first two months, I was injecting LL-37 whenever it was convenient—sometimes after breakfast, sometimes after dinner. My results were inconsistent at best. Some days I'd feel great, other days nothing.

Here's what I didn't understand: LL-37 absorption and activity are significantly affected by food, particularly fats and proteins. When you eat, your digestive enzymes and stomach acid are active, and if the peptide is circulating through your system during this time, it can get partially degraded before it reaches target tissues.

The fix: Inject on an empty stomach, ideally first thing in the morning or at least 3-4 hours after your last meal. I switched to morning injections about 20 minutes before breakfast, and the consistency of results improved dramatically. My tracking data showed that sinus congestion (which I rated daily on a 1-10 scale) averaged 3.2 with random timing versus 1.4 with morning fasted injections.

This is similar to what I learned with TB-500—timing matters way more than most people think.

Mistake #3: Terrible Reconstitution Technique

I cannot stress this enough: LL-37 is fragile. Like, really fragile. It's a 37-amino acid peptide with a specific tertiary structure that gives it antimicrobial activity. Shake it too hard, and you're basically injecting expensive dust.

When I first started, I was reconstituting my 5mg vials with bacteriostatic water (correct), but then I was shaking the vial to mix it faster (catastrophically wrong). I did this for probably six weeks before someone on a forum mentioned that you should never, ever shake peptides.

The proper technique:

I tested this by ordering two vials from the same batch. One I reconstituted properly, the other I shook like a martini. The shaken vial gave me basically zero results over two weeks. The properly reconstituted vial worked as expected. That was a $120 lesson in organic chemistry.

Mistake #4: Storage Like a Caveman

For my first month using LL-37, I kept my reconstituted vial in my gym bag. I work out at different times, and I figured it was easier to just keep everything together. Temperature in my car probably ranged from 65°F to 85°F depending on the day.

Guess what happens to a delicate antimicrobial peptide when it's exposed to heat? It degrades. Fast.

LL-37 should be stored:

After I started storing it properly—in my fridge, in a small cooler bag when traveling—the consistency improved again. I also started dating my vials with a Sharpie so I knew exactly how old each reconstituted solution was.

This is honestly similar to the storage issues I had early on with hexarelin. These compounds are sensitive, and if you treat them like you're storing creatine powder, you're going to have a bad time.

Mistake #5: No Cycling Strategy

I ran LL-37 continuously for seven months straight. Every single day, 300mcg, like clockwork. Around month five, I noticed the benefits started to diminish. My sinus issues came back, recovery wasn't as good, and I just generally felt like it wasn't working anymore.

What I didn't realize: your body can develop tolerance or reduced responsiveness to exogenous peptides, especially antimicrobial ones. There's also some evidence (admittedly limited) that continuous LL-37 supplementation might downregulate your natural production.

Better approach: Cycle it. I now run LL-37 for 8-12 weeks, then take 4-6 weeks off. Some people do 5 days on, 2 days off each week. The key is giving your system a break so it doesn't adapt.

When I switched to cycling (12 weeks on, 6 weeks off), I noticed that each new cycle felt almost as effective as the first time I used it. My tracking data backed this up—average wellness scores during week 1 of a new cycle: 7.8/10. During week 20 of continuous use: 5.1/10. During week 1 after a 6-week break: 7.6/10.

Bonus Mistake: Not Tracking Results

This isn't strictly a dosing mistake, but it cost me a lot of wasted effort. For the first three months, I had no systematic way of knowing if LL-37 was actually working. I just had vague feelings of "maybe better?"

I finally started keeping a simple spreadsheet tracking:

This data is what helped me identify the timing issue, the storage problem, and the tolerance development. Without it, I'd still be stumbling around in the dark.

What Actually Works: My Current Protocol

After three years of trial and error (and about $2,400 spent on LL-37), here's what I do now:

Results with this protocol: I've gone from 4-5 sinus infections per year to maybe one in the last 18 months. My recovery from training is noticeably better during LL-37 cycles. And I generally feel like my immune system is more resilient—I'm around sick people regularly and just don't catch stuff like I used to.

Is it all LL-37? Probably not. I also cleaned up my diet, started sleeping 7-8 hours consistently, and manage stress better than I did at 32. But based on my tracking data, the improvements correlate strongly with proper LL-37 use.

Frequently Asked Questions

How long does it take for LL-37 to start working?

In my experience, subtle effects start around day 5-7—better recovery, slightly less congestion. More noticeable immune benefits took 3-4 weeks. Don't expect overnight miracles. This is a gradual optimization, not a light switch.

Can you take LL-37 orally instead of injecting?

Technically yes, but bioavailability is terrible. It's a peptide, which means your digestive system will break it down before it can do much. Injectable (subcutaneous) is the standard route. I've never tried oral, and based on the research, I don't plan to—seems like a waste of money.

What are the most common side effects at proper doses?

At 300-500mcg daily, most people tolerate it well. I occasionally get mild injection site redness that resolves in a few hours. Some people report temporary acne if they dose too high. Rarely, people report fatigue or headaches, but I haven't experienced that personally. Always talk to your doctor before trying anything new.

Where do you actually buy LL-37?

I'm not going to recommend specific vendors because the peptide market changes constantly and I'm not trying to get anyone in trouble. Do your research, look for third-party testing (HPLC and mass spec), and be prepared to pay $80-150 per 5mg vial from reputable sources. If someone's selling it for $30, it's probably not what they say it is.

Final Thoughts: Is LL-37 Worth the Hassle?

Look, LL-37 isn't some magic bullet. It's not going to turn you into a superhuman overnight. But if you're dealing with recurring infections, immune dysfunction, or gut issues, and you've already handled the basics (sleep, diet, stress), it might be worth exploring.

The key is doing it right. Don't make the mistakes I made—start low, time it properly, handle it carefully, store it correctly, and cycle it intelligently. And for the love of all that is holy, track your results so you actually know if it's working.

I'm not a medical professional, this is just my personal experience over three years of experimentation. Your results may vary. Always talk to your doctor before trying anything new, especially if you have existing health conditions or take medications.

But if you do decide to try LL-37, hopefully you can skip the $800 worth of mistakes I made and get straight to the good stuff.