Semaglutide with B12 dosage and evidence
Written by Aaron CuhaReviewed Sep 2026
The short answer
Semaglutide with B12 is a pharmacy-made premix where the B12 dose is set by the semaglutide dose, not by anyone's B12 level.
Evidence grade for Semaglutide with B12: Limited. The rule: people have taken it in a published study, but fewer than 100 of them. The sum on this page: 2 completed trials, none stating how many people. A grade counts how much has been done to people, not whether it works.
- People given it
- 0
- Human studies
- 2
- Found nothing
- 0
Dose
No human dose established
Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose.
2 completed trials, 0 people given it
7 effects reported, 5 unwanted, 2 wanted, by people using it, not a trial
Goal pages: Fat loss and metabolism, Gut health
In plain English
In plain English, from Aaron
This is how I would explain it to a friend. The evidence, with the numbers, is further down the page.
This is compounded semaglutide with vitamin B12 mixed in. The pitch is that the B12 helps with the nausea and the tiredness. Here is what actually happens. The B12 is set by your semaglutide dose, not by your B12 level. So it goes up every time you titrate, whether you need it or not.
What people take it for
- Losing weight.
- Less nausea from the shot.
- More energy.
- Some people believe B12 helps the drug work. Nobody has tested that.
What studies in people showed
Nobody has tested this mix. The semaglutide half is one of the best studied drugs on this site. In the STEP 1 trial, people lost 14.9 percent of their body weight in 68 weeks. The dummy shot group lost 2.4 percent. Half the drug group lost 15 percent or more. Nausea and diarrhoea were the main side effects. No vitamin was in that trial. The B12 half also has real trials, for a different job. In people with a proven B12 shortage, both pills and shots got over 90 percent of them back to normal in eight weeks. That is treating a shortage found by a blood test. Nobody has tested giving B12 to a person whose level is fine. Now the math, and it is odd. The B12 is held at 0.5 mg per mL no matter what. The semaglutide is either 1 mg per mL or 5 mg per mL. On the strong one, a 0.5 mg dose is 50 micrograms of B12. A 2.4 mg dose is about 240. On the weak one, that same 0.5 mg dose carries 250 micrograms. Five times the B12 for the same semaglutide.
What people report
Reports, not study results
The good
- Hunger goes quiet.
- Weight comes off.
The bad
- Nausea. It is the main report on any semaglutide, and it does not look smaller on the B12 versions.
- Constipation and reflux.
- Feeling tired early on, which people often blame on the drug when they are simply eating far less.
- Most people say they cannot tell the B12 versions apart from the plain ones.
- Dose confusion, because the same milligram number is a different volume on the two strengths.
Where these come from: The nausea and diarrhoea numbers come from the trial side effect tables. The comparison between B12 and plain versions comes from patient forums and is just people talking.
My bottom line
The semaglutide is the real thing. The B12 is along for the ride at a dose set by something that has nothing to do with your B12. If you want to know whether you need B12, the test costs almost nothing.
An opinion, not a finding. I am a coach, not a doctor.
What it has been measured to do
Measured in people
Goals Semaglutide with B12 has been tested for in people, biggest studies first. We count only what the studies on this page say, so the real numbers may be higher.
- Losing weightno headcount stated · 1 study
- Gut and digestionno headcount stated · 1 study
What people using it report
Real people telling you what happened to them. Nobody checked it, and the people who post are not a fair sample, so it cannot prove anything works. It is still the best guide on this page to what people actually do with Semaglutide with B12, what they expect, and what goes wrong. The full account, including the negative reports, is below.
33 of the 36 indexed goals have no study of any kind behind Semaglutide with B12
No study in people, animals or cells on this page reports a result for these. That does not prove Semaglutide with B12 does nothing for them. It does mean anything you have heard about Semaglutide with B12 and one of these did not come from a study cited here.
Show full evidence
What is Semaglutide with B12?
Semaglutide with B12 is a pharmacy-made premix where the B12 dose is set by the semaglutide dose, not by anyone's B12 level. The B12 stays at 0.5 mg/mL in every strength, while semaglutide comes at 1 or 5 mg/mL. So one strength gives five times more B12 per milligram of semaglutide than the other. No study has tested the mix. No study backs the reason the B12 is added.
Compounding pharmacies pair semaglutide with B12, in the form called cyanocobalamin. The reasons they give are that B12 helps with the sick feeling and the tiredness people get on a GLP-1 drug. Neither claim has a study behind it. What is true is that adding a vitamin makes the mix something other than a copy of the approved drug. That has mattered to pharmacies for legal reasons at times since the drug shortages ended.
The math is worth reading twice, because it is odd. In the common pharmacy strengths, B12 stays at 0.5 mg/mL. Semaglutide comes at either 1 mg/mL or 5 mg/mL, in 1 mL and 2.5 mL vials. On the 5 mg/mL mix, a 0.5 mg semaglutide dose is 0.1 mL. That holds 50 micrograms of B12. Step up to 2.4 mg and the dose is 0.48 mL, with about 240 micrograms of B12. On the 1 mg/mL mix, the same 0.5 mg of semaglutide is 0.5 mL. That holds 250 micrograms of B12. Five times as much B12 for the same semaglutide.
Three things follow that no label tells you. First, the B12 amount follows the semaglutide dose. It goes up every time you step up, and it has nothing to do with your B12 level. Second, two people on the same semaglutide dose, from two different strengths, get five times different B12. Third, someone starting at 0.25 mg on the strong mix gets 25 micrograms of B12 a week. For anyone who really needs B12, that is a tiny amount.
The semaglutide half has strong evidence in people. In the big STEP 1 study, average body weight fell 14.9% by week 68, against 2.4% on a dummy shot. That is a gap of 12.4 points. Half the semaglutide group (50.5%) lost 15% or more of their weight, against 4.9% on the dummy. Feeling sick and loose stools were the most common side effects. None of that study used B12.
The B12 half also has good evidence, for something else entirely. In a family doctor study, B12 pills and B12 shots into the muscle both brought B12 back to normal in well over 90% of people who were short of it, by eight weeks. That is topping up people who a blood test showed were low. It says nothing about giving B12 to someone whose level is normal.
How does Semaglutide with B12 work?
Semaglutide copies the gut hormone GLP-1. It slows how fast the stomach empties and turns down appetite, through the brain and the body. B12 is a vitamin used to fix a shortage. In someone who is not short of it, it does very little. Nobody has explained how B12 would ease GLP-1 nausea, and no study has tested it.
What have studies in people found about Semaglutide with B12?
Semaglutide has large studies in people. B12 top-ups have good studies in people. The mix has none.
- Semaglutide 2.4 mg weekly: in the STEP 1 study, average weight loss was 14.9% at 68 weeks, against 2.4% on a dummy shot.
- B12 top-ups: bring B12 back to normal in over 90% of people who are short of it by eight weeks, by pill or by shot.
- The nausea claim: no study has tested whether B12 eases the stomach side effects of GLP-1 drugs.
- The tiredness claim: no study has tested B12 against GLP-1 tiredness in people with normal B12.
- The premix: no published study and no listed trial of semaglutide mixed with B12.
What this does not tell you: Two well proven things in one syringe is not one well proven thing. The half that works for weight was tested with no vitamin. The half that works for a shortage was tested in people who were checked and found low.
What do people who took Semaglutide with B12 report?
This is what real people say happened to them, good and bad. Nobody measured it. A report cannot tell a real effect from the lift people get just from expecting it to work, from a diet or training change made at the same time, or from what was really in the vial. We still put it near the top. It is the next best thing to a study in people: what happens when real people use it, including what goes wrong.
- Feeling sick. This is the main report on any semaglutide, and it is not clearly any less on the B12 versions.
- Constipation and reflux.
- Tiredness early on. People often put this down to eating far less, not to the drug.
- No difference felt between the B12 and plain versions. This is the most common comparison people report.
- Confusion about the dose, because the same milligram number means a different amount of liquid on the 1 and 5 mg/mL strengths.
Sources: Trial side-effect tables supply the nausea and diarrhoea figures. The comparison between B12 and non-B12 preparations comes from forums including r/Semaglutide and telehealth patient communities, and is uncontrolled.
The state of the research
The honest reading is that the B12 is doing legal and sales work more than work in the body. Adding an ingredient makes the mix something other than an exact copy of the approved drug. That has mattered for what pharmacies may legally make. And B12 has a name for energy that sells well. For someone who really is short of B12, this is a fine way to get some while it lasts. But the amount is set by something unrelated, and it rises as the semaglutide dose is stepped up.
There is one real safety warning in this area, and it comes from the other weight loss drug. Lab tests of pharmacy-made tirzepatide plus B12 found a new unwanted chemical in many products. It forms when the peptide reacts with some forms of B12. That work was done by the maker of branded tirzepatide. That conflict should be stated and weighed, not used to wave the result away. And it tested tirzepatide, not semaglutide. Still, it is the only published chemistry on mixing this kind of peptide with B12, and it found a reaction.
The evidence, in charts
Fig. 1a · how many people
2studies in people cited, but none says how many people took part
number of people not stated
We do not draw a total, because none of the studies in people on this page gives one. Read the sources below for what each study measured.
We read the number of people from the source lines on this page. Where a line gives no number, we count nothing for it. We do not guess.
Fig. 1b · evidence mix
2 of 4 sources here are studies in people. The rest are not.
- Study in people · done in people250%
- Lab (cells in a dish) · cells or tissue125%
- Review of studies · sums up other studies125%
Counted from the list of sources on this page. It counts only what we cite, so there may be more studies out there. A review counts once, however many studies it sums up.
Fig. 2 · evidence over time
The studies cover 3 different years, 2020 to 2026, counted from the list of sources on this page.
Fig. 3 · legal status at a glance
US
Not approved
UK
Not approved
AU
Not approved
CA
Not approved
Not approved in any of the four countries shown. This is what the law says, not a verdict on the science. See Legal status below for the full text and any notes.
Fig. 4 · how much does what
Nobody has tested different amounts in people
This chart would show how the effect changes as the amount goes up. For this compound, nobody has measured that in people. So we leave it empty. We will not borrow an animal chart and pretend it works the same in people.
Fig. 5 · what the molecule is
- Kind of compound
- Blend
- Molecule weight
- Not on file
- Half-life
- Stated in words, not a numbersee the exact wording below
- Chain length
- None on file
Half-life as stated on file: Not defined for the mixture. The incretin component supports weekly dosing and the vitamin behaves as a vitamin, with no pharmacokinetic study of the combined preparation.
No amino acid sequence is on file for Semaglutide with B12, which is expected: a blend is not built from amino acids.
Fig. 6 · what is in the vial
We cannot show how much of each is in this blend
Sellers do not agree on a vial size for Semaglutide with B12, so nobody outside can know how much of each ingredient is in it. Splitting the bar evenly would make up the very number this page is here to question.
- SemaglutideStrong. At least two finished studies in people, and at least 1,000 people who took it. 12 completed trials, 42,363 people given it.amount not stated
- CyanocobalaminLimited. People have taken it in a published study, but fewer than 100 of them. 2 completed trials, none stating how many people.amount not stated
Ingredient list from the product labels we have. Amounts are what the label says is in the vial, never a dose.
The studies we cite
- Study in people2021Once-Weekly Semaglutide in Adults with Overweight or Obesity
Semaglutide caused large, well documented weight loss, and this is the study that showed it. Adults took a weekly 2.4 mg shot or a dummy shot for about 16 months. Average body weight fell 14.9% on the drug and 2.4% on the dummy, a gap of about 12 points. Half the drug group lost at least a sixth of their body weight, against one in twenty on the dummy. Feeling sick and loose stools were common, usually mild and short-lived. No vitamin was given with it.
STEP 1. Mean body weight changed by 14.9% with semaglutide 2.4 mg weekly against 2.4% with placebo at week 68, an estimated treatment difference of 12.4 percentage points. 50.5% of the semaglutide group lost 15% or more of body weight against 4.9% on placebo. Nausea and diarrhoea were the most common adverse events, usually transient and mild to moderate. Semaglutide alone; no vitamin was co-administered.
- Study in people2020Oral versus intramuscular administration of vitamin B12 for vitamin B12 deficiency in primary care: a pragmatic, randomised, non-inferiority clinical trial (OB12)
Swallowing B12 works as well as injecting it, in people who are truly short of it. People whose blood tests showed a shortage got either pills or shots into the muscle. After eight weeks both ways had brought blood levels back to normal in well over nine in ten people. The two groups ended within a point of each other. Notice who was studied. These were people proven low by a blood test, being topped back up.
In patients with documented B12 deficiency, both oral and intramuscular B12 normalised serum concentrations in well above 90% of patients at eight weeks, with the between-arm difference at that point under 1% by per-protocol analysis. This is what B12 evidence looks like: replacement in people shown by a blood test to be deficient.
- Review of studies2026FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss
This is the FDA's standing warning about pharmacy-made and other unapproved GLP-1 drugs. It covers reports of harm, dosing mistakes, and the fact that the FDA does not check pharmacy-made drugs for safety, whether they work, or quality.
FDA's standing statement on compounded and other unapproved GLP-1 products, covering adverse event reports, dosing errors and the fact that compounded preparations are not reviewed by the agency for safety, effectiveness or quality.
- Lab (cells in a dish)2026A novel, widespread impurity in mass-compounded tirzepatide/B12 products: potential patient safety implications
This is a lab test of pharmacy-made weight loss shots mixed with B12, bought from many US sources. The testers found a new unwanted chemical in them. It forms when the peptide reacts with some forms of B12. The test was done and written up by staff of Eli Lilly, the maker of branded tirzepatide. That is a conflict of interest. It is still the only published chemistry on these mixes. The samples were tirzepatide, not semaglutide.
Analytical testing of compounded incretin plus B12 products from multiple US market sources identified a previously unidentified impurity arising from a chemical reaction between the peptide and certain B12 analogues. The work was performed and authored by Eli Lilly employees, which is a disclosed and relevant conflict, and it is the only published chemistry on peptide plus B12 premixes. The samples tested were tirzepatide products, not semaglutide.
Where to buy Semaglutide with B12
No seller we track lists Semaglutide with B12 yet. We read sellers’ public product lists every week, and this section fills in as soon as one does. Every seller, graded
Common questions
Has Semaglutide with B12 been tested in people?
Yes. 0 people given it across 2 completed trials cited here, 0 of which found nothing. Semaglutide with B12 is a pharmacy-made premix where the B12 dose is set by the semaglutide dose, not by anyone's B12 level.
What is the Semaglutide with B12 dosage?
No human dose established. Amounts that were given in studies sit in Human evidence on this page. None of them is a personal dose. 2 completed trials, 0 people given it
Is Semaglutide with B12 FDA-approved?
Not an approved product. Pharmacy-mixed (compounded) products are not FDA approved. They are not checked for safety, for whether they work, or for quality. The FDA has also raised concerns about unapproved GLP-1 products sold for weight loss.
Does the B12 help with nausea?
No study has tested that. It is the reason given for the mix, and there is no proper evidence behind it.
How much B12 am I getting?
It depends on your semaglutide dose and your strength. B12 is fixed at 0.5 mg/mL. So on a 5 mg/mL semaglutide mix, a 0.5 mg dose holds 50 micrograms of B12, and a 2.4 mg dose holds about 240 micrograms. On a 1 mg/mL mix, the same 0.5 mg dose holds 250 micrograms.
Is that a sensible B12 dose?
It is not a dose set by anything about you. It is set by how much semaglutide you happen to take that week, and it goes up every time you step up. If you want to know whether you need B12, the blood test costs very little.
Is the combination approved?
No. Pharmacy-made drugs are not FDA approved. Nobody checks them for safety, whether they work, or quality. Semaglutide itself is approved. This mix is not.
Is there a chemistry problem with mixing a peptide and B12?
There is at least one published finding. Lab tests of pharmacy-made tirzepatide plus B12 found a new unwanted chemical in many products. It forms when the peptide reacts with some forms of B12. The tests were done by the maker of the branded drug, which is a real conflict of interest. And they looked at tirzepatide, not semaglutide.