I woke up with a nasty sore throat yesterday, so I skipped my usual espresso / cappuccino combo. By noon I felt the twinge of a headache coming on, which I presume was brought on by the lack of caffeine coursing through my system. Recently my espresso consumption is about double normal (3-5 doubles per day instead of 2-3). I've only experienced a minor tingling of a headache before attributable to my caffeine habit. Yesterday threatened a full-blown migraine (I didn't wait to find out and took some Excedrin Migraine, which includes a few hundred milligrams of caffeine).

Did I cross some threshold?

Welcome to the caffeine-junkie-club Dan!

Withdrawal symptoms at last!

I don't get it often, 'cause I drink coffee almost every day, but I do get it and it is pretty awful.
The other way I get it is by drinking drip-pot coffee.
I don't know why, but I get these intense migraines....

You said you were sick also; that doesn't help neither.
Your system is fragile and the need for caffeine is even worse when that happens.

I had some thyroid problems back in 1995 - just after I got a decent espresso machine. I had a condition called thyroiditis that causes one's thyroid gland to produce too much thyroid hormone, then not enough. According to my doctor the entrance of thyroid hormone into cells is under the influence of adrenal hormones. My doctor was also convinced that caffeine in large amounts could mess with normal adrenal function but I'm not going to get into that here.

Anyway I couldn't drink any coffee, no soda, nothing with caffeine as it made me feel like I was ODing on caffeine. I was shaky, speedy, elevated heart rate, sick to my stomach, yuk.

It was a temporary condition, thankfully, but I had horrid headaches for a week or so while getting "off" of coffee. I felt awful in the morning, I had serious cravings.

I was so happy once my thyroid gland got back under control. 6 months was a long time to look at my machine and wish I could use it.


Ann

When I hang an IV bottle under my PF and spend the morning laying on the floor in front of my machine while my 5-year-old son pulls shots for me, I hit the threshold.

If you drink because you want it as opposed to need it is the difference. During the summer my consumption drops to two or three doubles a day, in the winter that goes up to three or four doubles a day.

Thanks Dave, I will watch for those "early warning" signs.

Searching the web, I didn't find a firm answer to my question, i.e., at what consumption amount per day can one expect withdrawal symptoms like headaches and irritability. An interesting website by John Hopkins University entitled "Information About Caffeine Dependency" basically says there is no pat answer, it depends on the person. This excerpt caught my eye:

Many caffeine consumers may be unaware of their physical dependence on caffeine because their frequent habitual consumption precludes a period of sustained abstinence (e.g. 2 days). Furthermore, relatively low doses of caffeine (e.g. as little as 25 mg) can partially suppress withdrawal symptoms.

Or to put it another way for caffeine dependents, a "full dose" isn't required to avoid unwanted symptoms.

As you found, there is no set figure that would say that you have crossed over into caffeine dependency. In fact, habitual users (like us) can tolerate /enjoy caffeine levels that would make a non-coffee drinker quite ill. Withdrawal symptoms if you miss your morning fix are highly variable from person to person. You could probably ballpark it around 400mg/day for the average person, although there are reports of some people showing dependency on as little as 100mg (1 cup). The short answer to your query is that it varies widely based on your genetic background.

The average caffeine intake for coffee drinkers is about 280mg/day and the LD50 (lethal dose for 50% of people) is in the area of 18g [200mg/kg; assumes 90kg adult]. It'd take over a hundred cups to get near that amount.

Suicide by coffee, I will have to keep that one in mind.

I think the threshold is pretty high.

In high school I spent a lot of time hanging out in coffee shops and (gasp) Denny's. My usual consumption for one night would be 2-3 16 oz coffees at the local shop, then about 8-15 cups at Denny's (no joke). All this between the hours of 7pm and 2 am.
I'd usually crash and go to bed soon after that, somehow not feeling the effects of the caffeine rushing through my system.

I did, however, have some strange effects after a whole summer of doing this every night....when school started back up, I wasn't able to go to the Denny's or local shops as much, so I drank far less coffee. I didn't put it togther that I always had a strange twitch in my left eye before I had my coffee in the morning. I never got headaches or anything, just the twitching that went away after a cup or two.
I've since cut back (slightly).

I read that you can even get addicted to decaf. Depending on the bean/technique etc etc is has around a 25th of the caffeine of standard coffee. So it doesn't take much...

I usually drink about 5 shots of espresso by around 9:00 a.m. m-f. I get up early and have my first cup around 6 and my second between 8-9. On Saturdays if I sleep in (God willing!) and don't get up until 8 or so I experience a mild headache. I usually resolve this by having coffee and have no problems the rest of the day. If I do the same thing on Sunday I do not experience any headaches.
During the work week I also supplement my caffeine intake in the afternoon with another double or a "Energy Drink". Sometimes I don't have time to walk to the coffee shop. So maybe my total intake a day is around 7 shots.