--- title: "Peptide Dose Converter: mcg to mg, mg to mcg, and IU" description: "Convert peptide doses between mcg and mg, and between mg and IU for somatropin (1 mg = 3 IU). Learn why HCG and most peptides have no fixed IU factor." canonical: "https://www.vitalsvault.com/peptides/tools/dose-converter" last-updated: 2026-08-22 --- # Peptide Dose Converter: mcg to mg, mg to mcg, and IU > Convert peptide doses between mcg and mg, and between mg and IU for somatropin (1 mg = 3 IU). Learn why HCG and most peptides have no fixed IU factor. ![A Korean-American woman, 52, chin-length straight black bob with grey roots, no glasses writes a short note in a notebook at a café table](https://www.vitalsvault.com/_next/image?url=%2Fpublic-v3%2Fshoot%2Fpeptides%2Fhero-dose-converter.webp&w=3840&q=75&dpl=shadow-production-f0162cb4d465-40992538108-1) Peptide Guide · Free tools # Peptide dose converter mcg to mg and back for any peptide, and IU for somatropin, where a fixed standard exists. Weight1 mg = 1,000 mcg Somatropin1 mg = 3 IU (WHO standard) HCGNo fixed factor: use the IU on the label Micrograms mcg Milligrams mg International units IU IU is off for this setting: most peptides are dosed by weight and have no IU value. Pick somatropin to convert IU. The short answer One milligram (mg) is 1,000 micrograms (mcg), so divide mcg by 1,000 to get mg. IU measures biological activity, not weight, so it converts to mg only where a fixed standard exists. For somatropin (human growth hormone), 1 mg equals 3 IU. HCG has no fixed factor; use the IU on the label. Medically reviewed by [Robert Lufkin, MD (opens in a new tab)](https://www.robertlufkinmd.com/) Chief Medical Officer, Vitals Vault · Updated October 29, 2026 · 4 sources This calculator converts a dose your clinician has already set into a syringe reading. It does not choose a dose, check whether a product is right for you, or replace your pharmacy’s instructions. Always follow the label and the clinician who prescribed it. ## How mcg, mg and IU relate ### Weight: mcg and mg 1 mg = 1,000 mcg, and 1 g = 1,000 mg. 250 mcg is 0.25 mg; 3.21 mg is 3,210 mcg. These hold for every substance.[1](https://www.vitalsvault.com/peptides/tools/dose-converter#source-nist-si) ### Activity: IU An international unit measures biological effect against a reference standard, so its weight differs from one substance to the next. Never borrow one product’s IU factor for another. ### Where IU converts Somatropin has a fixed standard: 1 mg = 3 IU, so 3.21 mg is 9.63 IU. HCG is labeled in IU from a bioassay with no single mg factor, so use the IU on the label.[2](https://www.vitalsvault.com/peptides/tools/dose-converter#source-nibsc-somatropin)[3](https://www.vitalsvault.com/peptides/tools/dose-converter#source-dailymed-somatropin)[4](https://www.vitalsvault.com/peptides/tools/dose-converter#source-dailymed-hcg) ### From conversion to syringe units Converting is step one. To turn a dose into a reading on an insulin syringe you also need the vial strength and how much liquid it was mixed with. The [peptide dosage calculator](https://www.vitalsvault.com/peptides/tools/dosage-calculator) does both and shows the draw on a U-100 scale. ## Get the free Peptide Tracking Toolkit An Excel workbook that does the vial math, keeps your plan apart from what you actually took, tracks site rotation and flags dates to review, plus a short PDF guide for before you start. ### Workbook: 14 tabs - Start here - Dashboard - Vials - Schedule - Administration log - Site rotation - Wellness - Labs - Storage - Travel - Clinician questions - Provider and pharmacy - Costs - Notes ### Starter guide (PDF) - Still deciding, or already using one - FDA-approved, compounded and research-use, explained - Questions to ask a prescriber - How to read a compounding pharmacy label - Storage basics - Travelling with a prescription - Which labs to baseline, and when to retest ## Measure before you start The math tells you what to draw. Only a blood test before you start, and a retest after, shows what a peptide changed for you. 1. TestA baseline panel at Quest Diagnostics. 2. DecideA licensed clinician reviews your history and results. 3. RetestThe same markers again, side by side. [Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) - [Liver enzymes (ALT)Checks the liver before and during any new prescription.](https://www.vitalsvault.com/biomarkers/alt) - [Kidney function (eGFR)Peptides are cleared through the kidneys, so a baseline is useful.](https://www.vitalsvault.com/biomarkers/egfr) - [HbA1cYour average blood sugar over about three months.](https://www.vitalsvault.com/biomarkers/hemoglobin-a1c) - [hs-CRPA blood marker of inflammation you can track before and after a course.](https://www.vitalsvault.com/biomarkers/hs-crp) ![A white man, 63, heavy-set, thin white hair, ruddy cheeks, wire glasses looks up from a paperback on a garden bench](https://www.vitalsvault.com/_next/image?url=%2Fpublic-v3%2Fshoot%2Fpeptides%2Ffaq-dose-converter.webp&w=3840&q=75&dpl=shadow-production-f0162cb4d465-40992538108-1) ## Dose converter questions How many mcg are in 1 mg? There are 1,000 micrograms (mcg) in 1 milligram (mg). To go from mcg to mg, divide by 1,000; from mg to mcg, multiply by 1,000. Is mcg the same as µg? Yes. µg and mcg both mean microgram. Pharmacies often write mcg so it is not misread as mg. Can IU be converted to mg for every peptide? No. IU measures biological activity against a reference standard. Only a substance with a fixed standard, such as somatropin at 3 IU per mg, converts reliably. Most peptides are dosed in mg or mcg and have no IU value. How many IU are in 1 mg of HGH? For somatropin (human growth hormone), 1 mg is 3 IU, the factor set by the WHO International Standard. So 4 IU is about 1.33 mg. Why does the converter not give an mg value for HCG? HCG is labeled in IU from a bioassay, and activity per mg differs between products and sources. A single mg factor would be wrong for some vials, so use the IU printed on your label. How does this fit with the dosage calculator? Convert first, then calculate. The dosage calculator takes the vial in mg and the dose in mcg or mg, and returns the units to draw on a U-100 syringe. Is this a dosing recommendation? No. It converts units only. Your dose comes from a licensed clinician, and the converter cannot check a product’s identity, purity or strength. ## Peptides, prescribed and measured Vitals Vault is opening peptide care that starts with your blood work, is prescribed by licensed US clinicians and ends with a retest. Join the waitlist to hear first. - Prescription only - Licensed US clinicians - Quest Diagnostics labs [Get early access to peptide care](https://www.vitalsvault.com/peptides-waitlist)[Start with 120+ lab tests · $99](https://www.vitalsvault.com/labs#plans) ## More peptide tools - [Peptide dosage calculatorVial mg, water and dose to units on a U-100 syringe.](https://www.vitalsvault.com/peptides/tools/dosage-calculator) - [Peptide Tracking ToolkitFree Excel tracker and a starter guide (PDF).](https://www.vitalsvault.com/peptides/tools#toolkit) - [Peptide GuideWhat each peptide is, what it is studied for, and typical doses in people.](https://www.vitalsvault.com/peptides) ## Keep reading [Full Peptide Guide](https://www.vitalsvault.com/peptides) - SermorelinA 29-amino-acid fragment of growth hormone releasing hormone, once FDA-approved as Geref and since discontinued. - TesamorelinAn FDA-approved growth hormone releasing factor analog (Egrifta) for excess abdominal fat in adults with HIV-associated lipodystrophy. - IpamorelinA five-amino-acid growth hormone secretagogue that mimics ghrelin, studied for its selective release of growth hormone. - CJC-1295A long-acting growth hormone releasing hormone analog, studied for raising growth hormone and IGF-1. ## Sources 1. 1. [NIST. Metric (SI) prefixes (opens in a new tab)](https://www.nist.gov/pml/owm/metric-si-prefixes) 2. 2. [NIBSC. WHO 2nd International Standard for Somatropin, code 98/574 (instructions for use) (opens in a new tab)](https://www.nibsc.org/documents/ifu/98-574.pdf) 3. 3. [DailyMed (NLM). Somatropin product labels (opens in a new tab)](https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=somatropin) 4. 4. [DailyMed (NLM). Chorionic gonadotropin product labels (opens in a new tab)](https://dailymed.nlm.nih.gov/dailymed/search.cfm?labeltype=all&query=chorionic+gonadotropin) Built by the Vitals Vault editorial team, medically reviewed by Robert Lufkin, MD, and updated October 29, 2026. General education, not medical advice. This calculator converts a dose your clinician has already set into a syringe reading. It does not choose a dose, check whether a product is right for you, or replace your pharmacy’s instructions. 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