I Tracked My Caffeine for 30 Days—Here's What Happened to My Sleep

I thought I had my caffeine consumption under control. Two cups of coffee in the morning, maybe a third at 2 PM if I was dragging. Pretty reasonable, right?

Then I actually tracked it.

For 30 days, I logged every milligram of caffeine I consumed and monitored my sleep quality using a tracking app. What I discovered changed how I think about coffee—and more importantly, when I drink it.

The results weren't subtle. My sleep improved dramatically once I adjusted my caffeine timing, even though I didn't reduce my total intake. But the first week was rough.

Here's what happened when I tracked my caffeine religiously for a month, what surprised me, and the one change that made the biggest difference.

The Setup: Baseline Week (Days 1-7)

My typical routine before tracking:

• 7:00 AM: Large coffee (200mg caffeine)
• 10:00 AM: Second cup (150mg caffeine)
• 2:00-3:00 PM: Third cup if tired (150mg caffeine)
• Total: 350-500mg daily
• Bedtime: 10:30 PM

I used a sleep tracking app to measure:

• Time to fall asleep
• Number of wake-ups
• Total sleep time
• Sleep quality score (1-100)

Week 1 Results (Normal Routine):

• Average time to fall asleep: 28 minutes
• Wake-ups per night: 3-4 times
• Total sleep: 6.5 hours (in bed for 7.5 hours)
• Sleep quality score: 58/100
• Morning feeling: Groggy, needed coffee immediately

I also logged afternoon energy on a 1-10 scale. Without that 2 PM coffee, I'd hit a 3/10 around 2:30 PM.

The Experiment: Early Cutoff (Days 8-30)

New rule: Last caffeine by 12:00 PM sharp. No exceptions.

I kept my morning routine identical—same two cups, same times. The only change was eliminating afternoon coffee.

Days 8-11 (The Brutal Adjustment):

Not going to lie—this sucked. By 2:00 PM each day, I was absolutely dragging. My energy rating dropped to 2/10. I felt foggy, irritable, and useless.

What I tried instead of coffee:

• ✅ 20-minute power naps (helped significantly)
• ✅ 10-minute walks outside (surprisingly effective)
• ✅ Cold water on face (temporary boost)
• ❌ Sugary snacks (crash made it worse)
• ❌ Decaf coffee (still contains 5-15mg caffeine—felt wrong)

Sleep during this phase:

Even though days were rough, sleep immediately started improving:

• Time to fall asleep: 22 minutes (down from 28)
• Wake-ups: 2-3 per night (down from 3-4)
• Sleep quality score: 64/100 (up from 58)

The Turning Point: Week 2 (Days 12-18)

This is where things got interesting. By day 12, the afternoon crash started to diminish. My body was adjusting.

By day 15, I didn't even think about wanting coffee in the afternoon. My natural energy rhythm had shifted.

Sleep metrics Week 2:

• Time to fall asleep: 18 minutes (10 minutes faster than baseline)
• Wake-ups: 1-2 per night (down from 3-4)
• Total sleep: 7 hours (up from 6.5 hours)
• Sleep quality score: 72/100 (up 24% from baseline)
• Morning feeling: Actually refreshed

The Data That Surprised Me

I exported my sleep app data and compared Week 1 vs. Week 2. Here's what stood out:

The deep sleep improvement was the most shocking. I was getting nearly 50% more restorative deep sleep just by cutting out afternoon caffeine.

Weeks 3-4: The New Normal (Days 19-30)

By week 3, the new routine felt completely natural. I no longer craved afternoon coffee. My energy stayed relatively stable from 1:00-5:00 PM—not peak performance, but manageable.

Final week averages (Days 25-30):

• Time to fall asleep: 15 minutes
• Wake-ups per night: 1 (sometimes zero)
• Total sleep: 7.2 hours
• Sleep quality score: 81/100
• Morning energy: 8/10 (rarely needed to snooze alarm)

The Unexpected Benefits

Beyond better sleep, I noticed:

1. Less morning coffee needed - One cup now does what two used to
2. More stable energy - Fewer dramatic crashes and spikes
3. Better mood - Less irritability in the afternoon
4. Sharper focus - Especially in morning hours
5. Reduced caffeine dependence - Felt less "addicted"

What I Learned About Caffeine Timing

The Half-Life Reality Check

Before this experiment, I didn't fully appreciate caffeine's 5-hour half-life. A 150mg coffee at 2 PM means:

• 7 PM: 75mg remaining (half a cup)
• 10:30 PM: ~55mg remaining (more than a shot of espresso)
• Midnight: ~40mg remaining (still blocking sleep signals)

No wonder I was taking 28 minutes to fall asleep and waking up multiple times. My brain was fighting against active caffeine trying to keep me alert.

The One Change I'll Keep Forever

If I could only keep one change from this experiment, it's this: No caffeine after 12 PM.

I've since experimented with having occasional afternoon coffee on weekends when sleep timing is less critical. But on workdays, the 12 PM cutoff is non-negotiable. The sleep quality difference is too significant to ignore.

Is It Worth It?

The first week was genuinely difficult. But by week 2, it was worth it. By week 4, I couldn't imagine going back.

Better sleep improved everything: mood, focus, energy, productivity, even workout recovery. All from just shifting caffeine timing—not eliminating it entirely.

Sources & Further Reading

1. Drake C, Roehrs T, Shambroom J, Roth T. Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine. 2013;9(11):1195-1200. View study
2. Roehrs T, Roth T. Caffeine: Sleep and daytime sleepiness. Sleep Medicine Reviews. 2008;12(2):153-162.
3. Landolt HP. Sleep homeostasis: A role for adenosine in humans? Biochemical Pharmacology. 2008;75(11):2070-2079.

Last updated: January 2026