alt=A menstrual disc and mentrual bell are held next to each other. The disc is larger in diameter and flatter. It has a similarly thick rim and thinner material in the basin.|thumb|214x214px|Left: blue bell-shaped thick-walled menstrual cup (also called a menstrual bell); right: pink bowl-shaped thin-walled cup (also called a menstrual disc or ring). Note crumpling of the ring-shaped cup.
A menstrual cup is a menstrual hygiene device which is inserted into the vagina during menstruation. Its purpose is to collect menstrual fluid (blood from the uterine lining mixed with other fluids). Menstrual cups are made of elastomers (silicone rubbers, latex rubbers, or thermoplastic rubbers). A properly fitting menstrual cup seals against the vaginal walls, so tilting and inverting the body will not cause it to leak.
Menstrual cups come in two types. The older type is bell-shaped, often with a stem, and has walls more than thick. while bell-shaped cups come in sizes of ~31-53mm external diameter and as long as the wearer's cervix height permits. Menstrual cups are not meant to prevent pregnancy.
Every 4–12 hours (depending on capacity and the amount of flow), the cup is emptied (usually removed, rinsed, and reinserted). After each period, the cup requires cleaning. One cup may be reusable for up to 10 years, making their long-term cost lower than that of disposable tampons or pads, though the initial cost is higher. As menstrual cups are reusable, they generate less solid waste than tampons and pads, both from the products themselves and from their packaging.
Reported leakage for menstrual cups is similar or rarer than for tampons and pads. defecate, sleep, swim, do gymnastics, However, incorrect placement or cup size can cause leakage.
Terminology
thumb|upright=2|Cross-sectional diagram showing the [[uterus, cervix, fornix on either side of the cervix, vagina, and pubic bone. Ring-shaped cups lie in the upper portion of the vagina, with the inner edge in the posterior fornix and outer one held in behind the pubic bone, within the pelvic floor.]]
The terminology used for menstrual cups is sometimes inconsistent. This article uses "menstrual cup" to mean all types, and for clarity, distinguishes the two main types as "bell-shaped" and "ring-shaped". <!--The thick-walled cups are bell-shaped, and they usually but not always have a rim somewhat thicker than the thick, springy body; they look like contraceptive cervical caps. The thin-walled cups are usually more bowl-shaped (the bowl may have a deep dimple, for grip). They have a springy rim which is much thicker than the membrane of the baglike body; they look like contraceptive diaphragms.
Some menstrual cups have solid, hollow, or ring-like protrusions called stems; on thick-walled cups, they are attached at the point of the bell, and on thin-walled cups they are attached to the rim.-->
The thick-walled bell-shaped cups are the older type, and the term "menstrual cup" is sometimes used to refer only to bell-shaped cups. But in modern formal contexts, such as academic research "menstrual cup" usually refers to both types.
The US Food and Drug Administration holds that "A menstrual cup is a receptacle placed in the vagina to collect menstrual flow." The EU legislated that "The product group 'reusable menstrual cups' shall comprise reusable flexible cups or barriers worn inside the body whose function is to retain and collect menstrual fluid, and which are made of silicone or other elastomers."
Ring-shaped cups are also called "menstrual discs" and sometimes "menstrual rings", to distinguish them from bell-shaped cups. Bell-shaped cups are sometimes called "menstrual bells".
Because bell-shaped cups are commonly depicted as being placed in the vaginal canal, well below the cervix, they are also called "vaginal cups", with the ring-shaped cups called "cervical cups". This may not clearly reflect their position in the body. MRI imaging suggests that, contrary to some manufacturer's depictions, the bell-shaped cups called "vaginal cups" are placed over the cervix, in a position similar to a cervical cap (not to be confused with a cervical cup). Ring-shaped cups, called "cervical cups", also cover the cervix, but have one edge next to the cervix, and the other located further down the vagina, so that the cup is nearly parallel to the long axis of the vagina. and were similar external catamenial sacks of "canoe-like form", which in turn were similar to catamenial sacks which were waterproof rubber undersheet supports for absorbent pads. These were made from india-rubber or gutta-percha, forms of latex. Disposable and reusable pads do not demand the same hand hygiene, though reusable pads also require access to water for washing out pads.
If the hands have come into contact with any chemical that directly trigger sensory receptors in the skin, such as menthol or capsaicin, all traces of the chemical should be removed before touching the mucous membranes.
A UN spec recommends that cups should not be shared; they should only ever be used by one person.|alt=The punchdown fold has one point on the rim turned inside-out and tucked down below the opposite side of the rim. The 7 fold has the rim flattened into a line, and both layers in parallel folded at about halfway, such that one end of the line (one folding-point of the rim) is pressed against the middle of the side of the cup. The downpressed side runs diagonally, and the other side runs horizontally, making it look like the digit seven. The C fold is the simplest and bulkiest: the rim is flattened, and then folded in half, so that the two fold-points of the rim are together. From the end, it looks like a letter C.
Menstrual cup use 10.1177 17455065211058553-fig1 (cropped to insertion single frame).jpg|The folded menstrual cup is inserted and allowed to pop open. Pinching the sides of the cup together and positioning it for insertion.
Stap2 cropped.png|After the pinched cup is inserted, the outer edge of the cup is tucked behind the pubic bone, opening out the cup. The inner edge of the cup must cover the cervix.
</gallery>|border=no|align=right|caption=Ring-shaped menstrual discs are worn in the same position as a contraceptive diaphragm.
The vagina is narrowest at the entrance and becomes wider and easier to stretch further in. In some cases, the user may need to twist the cup or flex the vaginal muscles to ensure the cup is fully open.
In practice, the rim of a bell-shaped cup generally sits in the vaginal fornix, the ring-shaped hollow around the cervix. Those with deeper fornixes may use insertion techniques such as inserting the cup partway, opening it before the rim passes the cervix, and then pushing it up into place; or they may press the cup to one side and let it open slowly, the rim slipping over the cervix. If correctly sized and inserted, the cup should not leak or cause any discomfort. The stem should be completely inside the vagina. If it can't be positioned inside, the cup can be removed and the stem trimmed. Ring-shaped cups with non-circular rims are designed to be inserted with the widest, deepest part going in first. If they are inserted the wrong way around they may leak. If there are stems or other removal aids, they should be on the end inserted last.