Tri-Lo-Mili is a prescription birth control pill that contains two hormones, norgestimate and ethinyl estradiol, in a 28-day pack. It’s a triphasic, low-dose oral contraceptive, meaning the hormone levels change across three weeks of active pills rather than staying the same. It is a generic equivalent of Ortho Tri-Cyclen Lo.
How the 28-Day Pack Works
Each pack of Tri-Lo-Mili contains 21 active hormone pills and 7 inactive (inert) pills. The active pills are color-coded so you can tell which week you’re in:
- Days 1 through 7 (white pills): 0.180 mg norgestimate and 0.025 mg ethinyl estradiol
- Days 8 through 14 (pale blue pills): 0.215 mg norgestimate and 0.025 mg ethinyl estradiol
- Days 15 through 21 (blue pills): 0.250 mg norgestimate and 0.025 mg ethinyl estradiol
- Days 22 through 28 (green pills): No hormones
The estrogen dose stays constant at 0.025 mg throughout all three active weeks, which is on the lower end for combination pills. The progestin (norgestimate) gradually increases each week. This stepwise design is meant to more closely mimic natural hormone fluctuations, which some people find causes fewer side effects than a fixed-dose pill. Your period typically arrives during the green pill week.
How It Prevents Pregnancy
Tri-Lo-Mili works primarily by stopping ovulation. When you take the hormones consistently, your body doesn’t release an egg each month. The progestin component also thickens cervical mucus, making it harder for sperm to reach an egg, and thins the uterine lining.
With typical use, about 7 out of 100 people using combination pills like Tri-Lo-Mili become pregnant in the first year. That “typical use” number accounts for real-life slip-ups like missed pills or late starts. Taking your pill at the same time every day brings the failure rate significantly lower.
Common Side Effects
The most frequently reported side effects in clinical trials (occurring in at least 2% of users) include headaches or migraines, nausea or vomiting, breast tenderness, abdominal pain, irregular bleeding or spotting, mood changes, acne, vaginal infections, bloating, weight gain, and fatigue. Many of these are most noticeable in the first two to three months as your body adjusts, and they often improve with continued use.
Breakthrough bleeding or spotting between periods is especially common in the early cycles. It doesn’t mean the pill isn’t working, but if it persists beyond three months, it’s worth bringing up with your prescriber.
Serious Risks to Know About
Like all combination birth control pills, Tri-Lo-Mili carries a small but real risk of blood clots. The risk of venous thromboembolism (a clot in a vein, often in the leg or lung) is 3 to 9 cases per 10,000 users per year. That risk is highest in the first year of use and when restarting after a break of four weeks or longer. For context, pregnancy itself raises blood clot risk as much or more than the pill does.
Combination pills also slightly increase the risk of stroke and heart attack, particularly if you have other risk factors like high blood pressure, diabetes, or a history of migraines with aura. Smoking while on the pill is especially dangerous. The risk of serious cardiovascular events rises with age and the number of cigarettes smoked, and combination pills are not recommended for smokers over 35.
Other serious but uncommon risks include elevated blood pressure (more likely with long-term use), gallbladder disease, liver problems, and changes in blood sugar or cholesterol levels. People with a history of depression should pay attention to mood changes, since hormonal contraceptives can sometimes worsen depressive symptoms.
What to Do if You Miss a Pill
If you miss one active pill, take it as soon as you remember and then take the next pill at your usual time, even if that means two pills in one day. No backup contraception is needed for a single missed pill.
If you miss two active pills during week 1 or week 2, take two pills as soon as possible and two more the next day, then continue the pack normally. Use a backup method like condoms for seven days.
If you miss two pills in week 3, or three or more pills in any week, throw out the rest of the pack and start a new one that same day. Use backup contraception for seven days. The green pills in week 4 contain no hormones, so missing those has no effect on pregnancy protection.
Who Should Not Take Tri-Lo-Mili
This pill is not appropriate for everyone. It is specifically contraindicated for people who smoke and are over 35, those with a history of blood clots or stroke, people with certain types of heart disease or uncontrolled high blood pressure, those with a history of breast cancer or other estrogen-sensitive cancers, and anyone with liver tumors or active liver disease. Liver tumors linked to combination pill use are rare (estimated at about 3.3 cases per 100,000 users), but they can be serious.
If you have a history of migraines with visual disturbances, or if you’re planning surgery that will keep you immobilized for an extended time, your prescriber may recommend a different contraceptive method.