Check before you startThis one has documented interactions with medication classes where the consequences are serious. If you take any prescription medicine, run it past a pharmacist before starting.
How long to take it
Situational. Tolerance to the performance effect builds within weeks.
Who it's actually for
Most adults, in moderation. Not for children.
Safe upper limit
Reported400 mg per day for most adults; 200 mg in pregnancy
Powdered caffeine has caused deaths from measurement errors. Teaspoon quantities are lethal.
Health Canada's own published guidance — the right primary source for this market, but the live page should be re-pulled to confirm figures haven't been revised.
Interactions to know about
- Blood pressure medication — Beta blockers, calcium channel blockers, ACE inhibitors
- Antidepressants — SSRIs, SNRIs, MAOIs, tricyclics
- Antibiotics — Especially tetracyclines and quinolones
- Thyroid medication — Levothyroxine, carbimazole, methimazole
- Lithium — Mood stabiliser — narrow safety window
Other supplements:
Run your full list through the interaction check.
Practical notes
- Never measure bulk caffeine powder by eye.
- A half-life of five to six hours means an afternoon coffee is still working at bedtime.
- Stacks with pre-workouts, energy drinks and fat burners — count the total.