I have been taking 400mg of tramadol Hcl per 24 hour period since 2006. My daily dose is two – 50mg tablets (100mg) every 6 hours or four times a day. My MD informed me that 400mg per day is the max dose for adults under 70 years of age.
https://www.drugs.com/answers/maximum-dose-tramadol-you-24-hours-3506672.html

