Pick the injection you have and the date you had the last one. The tool works out when the next one is due, how late you can be without needing extra contraception, and the next few dates after that. The rules come from the CDC US Selected Practice Recommendations for DMPA (Depo-Provera, Sayana Press, depo-subQ provera 104) and the NHS pages for the contraceptive injection for Noristerat.
Depo shot calculator
Last injection → next shot due
Your last injection
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How this is worked out
For Depo-Provera (DMPA, including Sayana Press and depo-subQ provera 104) the next shot is due 13 weeks (91 days) after the last one. The CDC US SPR says it may be given up to 2 weeks late — up to 15 weeks (105 days) from the last injection — without needing extra contraception, and there is no limit on how early it can be given. If more than 15 weeks have passed, the CDC says the injection may be given if it is reasonably certain you are not pregnant; use condoms or abstain for the next 7 days and speak to your clinician.
For Noristerat (norethisterone enantate, UK) the next shot is due 8 weeks (56 days) after the last one. The NHS says the injection lasts 8 to 13 weeks depending on type and the leaflet, so this tool does not show a grace period for Noristerat. Ask your clinic what to do if you are late.
The rule for each type
| Injection | Normal gap | Grace period (no extra contraception needed) |
|---|---|---|
| Depo-Provera / DMPA (incl. Sayana Press, depo-subQ provera 104) | 13 weeks (91 days) | Up to 2 weeks late (15 weeks / 105 days from last) |
| Noristerat (UK) | 8 weeks (56 days) | Not stated — ask your clinic |
If you are late
If you miss the window, the NHS advice is to use condoms until you get your injection and for 7 days afterwards. You may need emergency contraception; speak to a pharmacist, sexual health clinic or GP (or your clinician in the US). The tool only flags that you are past the window; the decision is not its to make.
What this cannot do
This is a reminder-planning tool. It does arithmetic from the dates you type in, and it does not know your medical history or what your clinician would say. Starting after birth, switching from another method, or starting after a miscarriage or abortion all have their own rules; follow your leaflet or ask a doctor, nurse or pharmacist. No contraception prevents pregnancy for sure.
Setting the reminders
Once you know your due date, Doz keeps the injection date and your other medications in one place. For related arithmetic see the refill date calculator for prescriptions and the dose interval calculator for “every N hours” schedules.
Common questions
When is my next Depo shot due?
13 weeks (91 days) after the last one for Depo-Provera, Sayana Press and depo-subQ provera 104. Noristerat is 8 weeks (56 days) after the last one.
How late can I be for a Depo-Provera shot?
The CDC says Depo-Provera / DMPA can be given up to 2 weeks late, up to 15 weeks (105 days) after your last injection, without needing extra contraception. After that, use condoms or abstain for 7 days once you get the next shot, and speak to your clinician.
Can I have the shot early?
The CDC says there is no limit on how early DMPA can be given. Your clinic may still prefer a routine spacing, so check with them before you move the date in.
What if I miss the Depo window?
The NHS advises using condoms until you get your next injection and for 7 days afterwards. You may need emergency contraception; speak to a pharmacist, sexual health clinic or doctor (or your clinician in the US). Do not rely on this calculator for the decision.
How often is the Noristerat injection?
Noristerat (UK) is given every 8 weeks (56 days). The NHS says the injection lasts 8 to 13 weeks depending on the type and the leaflet, so if you are late, ask your clinic what to do rather than assuming you are still covered.
Does this calculator work for Sayana Press and depo-subQ provera 104?
Yes. Sayana Press and depo-subQ provera 104 are both DMPA at a lower subcutaneous dose, and they follow the same 13-week schedule with the same 2-week late window. Pick the Depo-Provera / DMPA option.
One thing this cannot do
This is an arithmetic tool, not medical advice. It works out numbers from what you type in — it does not know your medication, your prescription, or what you should do if something goes wrong. Anything about changing a dose, spacing doses differently, or handling a missed dose is a question for your doctor or pharmacist.