About Steroid Conversion Calculator
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Steroid Conversion Calculator: Corticosteroid Dose Equivalency Made Simple
TL;DR: Divide the current dose by its equivalency factor, then multiply by the target steroid's factor. For example, 10 mg of prednisone (equiv 5) equals 8 mg of methylprednisolone (equiv 4): (10 / 5) x 4 = 8. Equivalency values are based on anti-inflammatory potency relative to hydrocortisone at 20 mg.
Table of Contents
- Introduction
- When You Need Steroid Dose Conversion
- The Conversion Formula
- Step-by-Step Conversion Process
- Worked Examples
- Six Common Mistakes in Steroid Conversion
- FAQ
- Assumptions and Limitations
- Conclusion
- Further Reading
Introduction
Corticosteroids are among the most widely prescribed drug classes worldwide. Conditions ranging from autoimmune disease to respiratory emergencies to post-transplant immunosuppression all call for glucocorticoid therapy. The problem is that corticosteroids are not interchangeable milligram-for-milligram. Switching from one agent to another without adjusting the dose can result in undertreating inflammation or, worse, pushing a patient into adrenal crisis.
Standard equivalency tables exist for exactly this reason. They map the relative anti-inflammatory potency of each corticosteroid to a common reference point: hydrocortisone at 20 mg. A physician discharging a patient from IV dexamethasone to oral prednisone needs to know the correct crossover dose. A pharmacist verifying a prescription change should be able to confirm the arithmetic independently. And a patient reading their discharge paperwork should understand why their new tablet count looks different from the old one.
This calculator automates that arithmetic so the only thing left to verify is clinical judgment.
When You Need Steroid Dose Conversion
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Switching formulations during hospital discharge. A patient on IV methylprednisolone in the ICU transitions to oral prednisone before going home. The equivalent oral dose must maintain the same anti-inflammatory effect.
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Transitioning from high-potency to physiologic replacement. After prolonged dexamethasone therapy, a taper to hydrocortisone at physiologic doses (15-25 mg/day) requires accurate dose mapping to avoid adrenal insufficiency.
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Cross-referencing international prescriptions. Drug availability varies by country. A patient moving from a healthcare system that favors prednisolone to one that stocks prednisone needs confirmation that 5 mg of either agent is bioequivalent.
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Comparing clinical trial protocols. Research papers report steroid doses using different agents. Converting all reported doses to a single reference steroid makes it possible to compare treatment intensity across studies.
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Adjusting for formulary restrictions. Insurance formularies and hospital drug lists sometimes mandate substitution. When methylprednisolone is unavailable, the prescriber must calculate the equivalent dose of an alternative.
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Educating patients about dose changes. A patient taking prednisone 20 mg daily who is switched to dexamethasone 3 mg may worry that their dose was "cut." Showing the equivalency math reassures them that the anti-inflammatory coverage is the same.
The Conversion Formula
Equivalent Dose = (Input Dose / From Equivalency) x To Equivalency
Standard equivalency values (mg per unit of anti-inflammatory potency):
Hydrocortisone: 20 mg
Cortisone: 25 mg
Prednisone: 5 mg
Prednisolone: 5 mg
Methylprednisolone: 4 mg
Triamcinolone: 4 mg
Dexamethasone: 0.75 mg
Betamethasone: 0.6 mg
Each value represents the dose in milligrams that produces an anti-inflammatory effect equivalent to 20 mg of hydrocortisone. Lower numbers indicate higher potency. Dexamethasone at 0.75 mg is roughly 27 times more potent than hydrocortisone milligram-for-milligram.
Step-by-Step Conversion Process
Step 1: Identify the source steroid and dose. Record the current drug name and the dose in milligrams. Confirm whether the dose is per tablet, per administration, or per day.
Step 2: Look up the equivalency factor for the source steroid. Find its value from the table above. For prednisone, the factor is 5.
Step 3: Divide the dose by the source equivalency factor. This gives you the number of "equivalency units." For 10 mg prednisone: 10 / 5 = 2 units.
Step 4: Look up the equivalency factor for the target steroid. For methylprednisolone, it is 4.
Step 5: Multiply the equivalency units by the target factor. 2 x 4 = 8 mg methylprednisolone.
Step 6: Verify clinical appropriateness. The calculator gives a mathematical equivalent. Clinical factors such as renal function, duration of therapy, mineralocorticoid activity, and half-life differences may require dose adjustment beyond what the formula produces.
Worked Examples
Example 1: Rheumatoid Arthritis Patient — Prednisone to Methylprednisolone
A 55-year-old woman with rheumatoid arthritis has been taking prednisone 15 mg daily. Her rheumatologist wants to switch her to methylprednisolone due to fewer gastrointestinal side effects.
| Step | Calculation | Result |
|---|---|---|
| Source dose | Prednisone 15 mg | 15 mg |
| Equivalency units | 15 / 5 | 3 units |
| Target dose | 3 x 4 | 12 mg methylprednisolone |
She will take 12 mg of methylprednisolone daily. This delivers the same glucocorticoid activity as her previous 15 mg prednisone dose. Her rheumatologist may round to the nearest available tablet strength if 4 mg tablets are dispensed (3 tablets = 12 mg, so no rounding is needed here).
Example 2: COPD Patient — Dexamethasone to Hydrocortisone Taper
A 38-year-old man hospitalized for a COPD exacerbation received dexamethasone 6 mg IV daily. His team is now converting him to oral hydrocortisone for a gradual taper before discharge.
| Step | Calculation | Result |
|---|---|---|
| Source dose | Dexamethasone 6 mg | 6 mg |
| Equivalency units | 6 / 0.75 | 8 units |
| Target dose | 8 x 20 | 160 mg hydrocortisone |
The equivalent hydrocortisone dose is 160 mg per day. Because physiologic cortisol production is approximately 15-25 mg per day, this confirms that 6 mg of dexamethasone represents a supraphysiologic dose. The taper plan will reduce hydrocortisone gradually over weeks, allowing the hypothalamic-pituitary-adrenal axis to recover.
Six Common Mistakes in Steroid Conversion
1. Treating milligrams as interchangeable across steroids. Swapping 10 mg of prednisone for 10 mg of dexamethasone delivers roughly 13 times the intended anti-inflammatory effect. Always convert through equivalency units.
2. Ignoring mineralocorticoid differences. The equivalency table addresses anti-inflammatory (glucocorticoid) potency only. Hydrocortisone and cortisone have significant mineralocorticoid activity causing sodium retention. Dexamethasone and betamethasone have essentially none. Switching from hydrocortisone to dexamethasone at an "equivalent" dose removes mineralocorticoid coverage entirely.
3. Forgetting half-life differences. Hydrocortisone has a biological half-life of 8-12 hours. Dexamethasone lasts 36-54 hours. A patient on three-times-daily hydrocortisone cannot simply take the total daily equivalent as a single dexamethasone dose without considering the prolonged suppression of the HPA axis.
4. Converting without confirming the dosing interval. A prescription for "methylprednisolone 4 mg" might mean 4 mg once daily, twice daily, or four times daily. Always confirm total daily dose before converting.
5. Rounding aggressively. Small rounding errors compound. Converting prednisone 7.5 mg to dexamethasone gives 1.125 mg. Rounding to 1 mg (a common tablet size) represents an 11% dose reduction. For a patient on a slow taper, that gap matters.
6. Applying the table to non-systemic routes. Equivalency values apply to oral and IV systemic administration. Topical, inhaled, and intra-articular corticosteroids have different bioavailability profiles and are not covered by this conversion.
Assumptions and Limitations
- Anti-inflammatory basis. All conversions reflect relative anti-inflammatory (glucocorticoid) potency. Mineralocorticoid activity is reported separately and not factored into dose calculations.
- Systemic administration only. Equivalencies apply to oral and intravenous routes. Topical, inhaled, and intra-articular preparations are excluded.
- Linear dose response assumed. The formula assumes proportional potency across dose ranges. At very high or very low doses, pharmacokinetics may deviate from linearity.
- Clinical judgment required. This tool provides a mathematical starting point. Patient-specific factors — including renal function, hepatic metabolism, concurrent medications, and HPA axis status — may require dose adjustment.
- Source data. Equivalency values from Meikle & Tyler, 1977, American Journal of Medicine.
Conclusion
Steroid dose conversion is straightforward arithmetic wrapped around a single concept: different corticosteroids deliver different amounts of anti-inflammatory effect per milligram. The equivalency table reduces the comparison to a common reference point, and the formula handles the rest. Where this gets clinically significant is in the details that the formula cannot capture — mineralocorticoid effects, half-life mismatches, HPA axis suppression risk, and individual patient variability. Use the calculator for the math, and rely on clinical training for everything the math leaves out.