Compounded semaglutide with B12 (cyanocobalamin), and similar mixes with vitamin B6, glycine or niacinamide, have no clinical evidence of added benefit. No randomized trial has compared semaglutide plus B12 with semaglutide alone. A 2026 review of 33 compounded products found nearly half contained such add-ins and concluded there was “little justification” for adding nutrients.[1] FDA treats some of these combinations as essentially copies of approved drugs.[2]
For the basics of how GLP-1 drugs work, see our GLP-1 basics hub and the semaglutide profile.
What is in these compounded products?
Compounded drugs are mixed by pharmacies rather than made by a drug company and approved by FDA. Researchers who searched compounding pharmacy websites in early 2025 found 33 semaglutide or tirzepatide products that differed from the approved versions:[1]
- 48% contained semaglutide or tirzepatide combined with one or more of cyanocobalamin (B12), glycine, niacinamide (a form of vitamin B3), docusate (a stool softener) or ondansetron (an anti-nausea drug).
- The other products were single-ingredient sublingual drops or dissolving tablets.
- Only 18% listed a beyond-use date and storage instructions together.
Vitamin B6 (pyridoxine) is another add-in some people ask about. We found no published randomized trial testing semaglutide or tirzepatide combined with any of these ingredients.
Does B12 add anything to semaglutide?
There is no evidence that it does.
- Weight loss: approved semaglutide 2.4 mg produced 14.9% average weight loss in STEP 1 without any vitamin added.[8] The only published study of a semaglutide-B12 product was a retrospective review of 94 people at a commercial wellness studio, who lost an average of 4.6% of body weight at 3 months.[4] It had no comparison group, so it cannot show whether B12 changed anything.
- Dose of B12: in that study, the B12 dose was tiny, starting at 0.125 mg and rising to 0.24 mg alongside the semaglutide.[4]
- Side effects: no study shows B12 reduces nausea, fatigue or hair loss on GLP-1 drugs.
B6, glycine and niacinamide
| Additive | What it is | Evidence for adding to a GLP-1 |
|---|---|---|
| Vitamin B12 (cyanocobalamin) | Vitamin needed for nerves and red blood cells | No trial of the combination; one uncontrolled study[4] |
| Vitamin B6 (pyridoxine) | Vitamin sometimes used for pregnancy nausea | No published trial with semaglutide or tirzepatide |
| Glycine | Amino acid | No published trial; little justification found[1] |
| Niacinamide | Form of vitamin B3 | No published trial; little justification found[1] |
| Ondansetron | Prescription anti-nausea drug | Rationale exists, but no evidence for this injected use[1] |
Why these combinations exist: the FDA rules
FDA declared the semaglutide shortage resolved on February 21, 2025, and the tirzepatide shortage earlier.[2] Once a drug is off the shortage list, compounders face tighter limits:
- State-licensed pharmacies (503A): the grace period for making copies of semaglutide injection ended in April 2025.[2] They generally may not make drugs that are “essentially a copy” of an approved product.
- Outsourcing facilities (503B): the grace period ended May 22, 2025.[2] As of April 2026, semaglutide and tirzepatide were not on the 503B bulks list or the drug shortage list.[2]
FDA addressed B12 directly. It may consider a compounded injection combining semaglutide and B12 to be essentially a copy of approved products when both are given by the same route and the amounts of each are within 10% of the strengths of commercially available products.[2] The exception is when a prescriber determines and documents that the change makes a significant difference for an identified individual patient.[2]
In February 2026, FDA announced it intends to restrict GLP-1 active ingredients intended for non-approved compounded drugs. It also said companies cannot claim compounded products are generic versions of approved drugs or the same as them.[6]
Safety concerns with compounded GLP-1s
FDA lists several concerns with compounded GLP-1 products:[3]
- Not reviewed: compounded drugs are not FDA-approved, and FDA does not check them for safety, effectiveness or quality before sale.
- Different salts: some products use semaglutide sodium or semaglutide acetate, which FDA says are different active ingredients from the approved drug, with no known lawful basis for compounding.
- Dosing errors: FDA has received reports of overdoses from people measuring doses wrongly from vials, some needing hospital care.
- Adverse event reports: as of May 31, 2026, FDA had received 990 reports for compounded semaglutide and more than 730 for compounded tirzepatide, likely an undercount.
The American Diabetes Association has also raised safety, quality and efficacy concerns about compounded GLP-1 products.[7] For a full comparison, see compounded semaglutide vs Ozempic.
When B12 actually matters: metformin
There is one real B12 issue for many GLP-1 users: metformin. Many people with type 2 diabetes take metformin with a GLP-1 drug.
In the long-term Diabetes Prevention Program Outcomes Study:[5]
- Low or borderline-low B12 affected 20.3% of metformin users vs 15.6% on placebo at 13 years.
- Each year of metformin use raised the odds of B12 deficiency by about 13%.
- Nerve damage (neuropathy) was more common in metformin users with low B12.
- The authors recommended considering routine B12 testing in people on metformin.
Low B12 can cause tiredness, anemia, or numbness and tingling in the hands and feet, but many people have no symptoms, which is why testing matters. If testing shows low B12, a clinician can treat it with standard B12 tablets or injections. There is no need for it to be mixed into a GLP-1 product, and a fixed add-in dose may not match what a deficient person needs.
The bottom line
Adding B12, B6, glycine or niacinamide to semaglutide or tirzepatide has no proven benefit. These combinations grew out of compounding rules, not clinical research. If you are concerned about B12, ask about a blood test, especially if you take metformin. For other GLP-1 questions, see GLP-1 nausea, GLP-1 hair loss and GLP-1 storage.
