Phentermine Hydrochloride 37.5mg plus 8mg?

Usual Adult Dose for Obesity
8 mg tablet (Lomira): 8 mg orally 3 times a day 30 minutes before meals

Some patients may only require 4 mg dose (one-half tablet) 3 times a day

15 and 30 mg capsules: 15 or 30 mg orally approximately 2 hours after breakfast

37.5 mg capsules and tablets (Adipex-P): 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast
Some patients may only require 18.75 mg (one-half tablet) orally once a day OR 18.75 mg orally twice a day

Comments:
Dosage should be individualized to obtain an adequate response with the lowest effective dose.
Late evening dosing should be avoided due to the possibility of insomnia.

Use: Short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction in the management of exogenous obesity in patients with an initial body mass index (BMI) of 30 kg/m2 or greater, or BMI of 27 kg/m2 or greater in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia).

https://www.drugs.com/dosage/phentermine.html#Usual_Adult_Dose_for_Obesity

I suggest you ask for a second opinion.