Phentermine 15mg Dosing Schedule
Phentermine 15mg should be taken once daily, approximately 2 hours after breakfast, and the next dose should be given 24 hours later (the following morning). 1
Timing and Administration
The FDA-approved dosing regimen for phentermine is straightforward:
- Take once daily in the morning, specifically about 2 hours after breakfast 1
- Avoid late evening dosing due to the risk of insomnia, as phentermine's appetite-suppressing effects last 12-14 hours 1
- The next dose is simply taken the following morning at the same time
Dosing Considerations for 15mg
The 15mg dose represents the lower end of the therapeutic range (15-30mg daily) 1. This dose is particularly appropriate for:
- Patients with severe renal impairment (eGFR 15-29 mL/min/1.73 m²) - this is the maximum recommended dose 1
- Initial therapy in patients where tolerability is a concern
- Patients who may be sensitive to sympathomimetic effects
Alternative Dosing Regimen
While the standard approach is once-daily dosing, there is an FDA-approved alternative using 8mg tablets taken up to 3 times daily (approximately 30 minutes before meals), which can be titrated as low as 4mg 2. However, this does not apply to the 15mg capsule formulation you're asking about.
Important Timing Pitfalls
- Do not take in the late afternoon or evening - phentermine's stimulant properties will interfere with sleep 1
- Do not take on an empty stomach first thing in the morning - the recommended timing is 2 hours after breakfast 1
- Do not split or divide 15mg capsules - they are not designed to be opened or divided
Monitoring Schedule
While taking phentermine 15mg daily:
- Monitor blood pressure and heart rate regularly, as phentermine can cause modest increases 2
- Assess weight loss response at 12 weeks - if inadequate response, consider dose escalation to 30mg or discontinuation 2
The dosing is simple: one 15mg capsule every morning, 2 hours after breakfast, avoiding any evening administration.