What happens if you stop Phentermine or Wegovy?

Wegovy's label includes a trial that stopped the drug on purpose; Phentermine's does not, which is a difference in what is known rather than in what happens. On Wegovy's label, the people randomly assigned to stop gained 6.9% of body weight over the following 11 months while those who carried on lost 7.9% more. That figure belongs to Wegovy's trial, so this page does not apply it to Phentermine.

Is Phentermine or Wegovy better for weight loss?

Only Wegovy has a trial figure recorded here: 14.9% average weight loss, from its own label trial. Phentermine has none on this site, so the two cannot be compared on effect and this page does not pick one on it.

Which is cheaper, Phentermine or Wegovy?

Phentermine publishes no all-in monthly price that could be verified, so this page carries no comparison rather than an estimate — and an unpublished price is itself worth weighing.

Can you switch between Phentermine and Wegovy?

They are different molecules, so this is a change of medication rather than of brand, and the one you move to is started on its own dosing schedule.

← All providers and medications

Phentermine (generic) vs Wegovy (semaglutide injection)

Verdict

Neither comes out ahead on the axes compared here. Wegovy scores higher on the published halfrx formula, 6.9 against 3.1; the formula takes in more than this table does.

Computed from the stored fields, so it moves when a price does. Nothing here is written by hand or by a model.

Wegovy (semaglutide injection) or Phentermine (generic): which one has a price?

Only Wegovy (semaglutide injection) has an all-in figure here: $199–$399 a month, read from its own page on 2026-09-22. No price is published here for Phentermine (generic), so price cannot decide between them. Every axis below is computed from stored fields rather than written by hand, so the comparison moves when a price does. Neither carries an FTC action, a state action, a BBB F grade or an FDA warning letter. One is branded and the other generic, and they are different drugs, so the gap is the molecule as well as the price. The published formula scores them 3.1 and 6.9 out of 10, arithmetic over the same stored fields rather than an editor's preference. Cost here is scored on what a patient pays once titrated, never on the entry price, because an introductory rate covers the months before anybody has reached the dose they stay on.

Head to head

Phentermine (generic) against Wegovy (semaglutide injection), one row per axis, with the side that wins each axis marked.
What decides it	Phentermine price unverified	Wegovy $199–$399/mo
Entry priceNot comparable — Phentermine (generic) publishes no verified all-in price.	not comparable	not comparable
Regulatory and complaint riskNeither carries a lawsuit, an FDA warning letter or a supply-risk flag.	tied	tied

What the trials, the titration and a year actually say

Axis	Phentermine	Wegovy
The trial that figure comes from	The label does not carry a modern trial figure; it states in its own words that the usefulness of this class 'should be measured against possible risk factors', and it is not recommended for long-term use.	STEP 1, Study 2 on the label (NCT03548935), 68 weeks: 14.9% mean weight loss at 2.4 mg against 2.4% on placebo, intention-to-treat.
Maintenance dose	37.5 mg once daily, in the morning	2.4 mg once weekly, or 1.7 mg
Earliest week you reach it	—	week 17
Year one at the published price of every step	No titration prices recorded	$4,237

The year-one figures walk each titration step at its published price and count the thirteen fills a 28-day month bills. The full arithmetic is published.

Go to Phentermine ↗Go to Wegovy ↗

What separates these two, price aside

These are different molecules — phentermine against semaglutide — so this is a comparison of two treatments, not of two prices for one.

Multiple generic manufacturers

Phentermine (generic)

3.1

Price unverified

Controlled substanceWeaker moleculeNo published priceStrict dosing rules

Novo Nordisk

Wegovy (semaglutide injection)

6.9

$199–$399/mo all-in

verified 2026-09-22

Boxed warning

Phentermine (generic)

Pros

+Pharmacies acquire it at $0.068 a tablet, about $2 for a 30-day supply, under the federal NADAC survey. That is what a pharmacy pays, not what it charges you.[2]
+Covered by more Medicaid programs than any GLP-1 — seven states cover an older weight-loss agent while covering no GLP-1 at all.[3]
+One tablet each morning, no injection, no titration schedule beyond a possible half dose.[1]

Cons

−Approved for a few weeks only. Every monthly subscription selling it as ongoing therapy is using it off the label's own duration.[1]
−Schedule IV controlled substance, chemically related to the amphetamines, with the dependence warnings that follow from that.[1]
−Stopping after prolonged high dosing brings extreme fatigue and depression, per the label — which is a hard exit from a subscription that sold it as maintenance.[1]
−No cardiovascular outcome data of the kind the GLP-1s now carry, and contraindicated where blood pressure is uncontrolled.[1]

Sources

Wegovy (semaglutide injection)

Pros

+One flat $349 across every standard dose from 0.25 to 2.4 mg — no dose-escalation penalty and no refill deadline attached, unlike Lilly's conditional pricing on Zepbound.[1]
+New patients pay $199 for the first two fills through 31 December 2026 — the first two of the four titration months.[2]
+Approved for cardiovascular risk reduction, not only weight — the strongest insurance-coverage argument in the category.[1]
+The longest real-world safety record of any modern weight-loss GLP-1.[1]
+Commercially insured, the savings card can bring it to $25 a month, capped at $100 of savings per month.[2]

Cons

−$1,349 monthly list price without insurance or the self-pay program.[1]
−Weaker than tirzepatide where the two were tested head to head: in SURMOUNT-5, weight fell 13.7% on semaglutide against 20.2% on tirzepatide over 72 weeks.[6]
−A month is one box of four weekly pens, so a year takes 13 boxes, not 12: $4,537 at $349 rather than the $4,188 that 'per month' implies.[1]
−The new high dose, Wegovy HD 7.2 mg, sits outside the flat price at $399.[1]
−Weekly injection, refrigerated storage, GI side effects during titration, and weight regain after stopping is the documented norm.[3]

Sources

Phentermine side effects →Wegovy side effects →Phentermine dosage →Wegovy dosage →

Comparisons are computed from the fields on each card, not written by hand or by a model, so they change when the data does. Information only, not medical advice. halfrx may earn a commission from some links, which never changes what a comparison says.

Everything on Phentermine

Everything on Wegovy

Phentermine against Wegovy, answered

What happens if you stop Phentermine or Wegovy?: Wegovy's label includes a trial that stopped the drug on purpose; Phentermine's does not, which is a difference in what is known rather than in what happens. On Wegovy's label, the people randomly assigned to stop gained 6.9% of body weight over the following 11 months while those who carried on lost 7.9% more. That figure belongs to Wegovy's trial, so this page does not apply it to Phentermine.
Is Phentermine or Wegovy better for weight loss?: Only Wegovy has a trial figure recorded here: 14.9% average weight loss, from its own label trial. Phentermine has none on this site, so the two cannot be compared on effect and this page does not pick one on it.
Which is cheaper, Phentermine or Wegovy?: Phentermine publishes no all-in monthly price that could be verified, so this page carries no comparison rather than an estimate — and an unpublished price is itself worth weighing.
Can you switch between Phentermine and Wegovy?: They are different molecules, so this is a change of medication rather than of brand, and the one you move to is started on its own dosing schedule.