How long can vitamin C tablets not eat after opening?

The reference value of drug instructions
In general, the expiry date of vitamin C tablets after opening depends largely on the drug label. The stability of vitamin C tablets produced by different manufacturers may vary. Some instructions will clearly mark the use period after opening, for example, some may write that it is used within 3 months after opening. This is because after opening, the drug will come into contact with outside air, moisture and other factors, which may affect its quality.
Effects of preservation conditions
Humidity: If the storage environment humidity is high, vitamin C tablets are easy to get damp. In the appropriate humidity (relative humidity 40%-60%) environment, the stability of vitamin C tablets will be better. However, if it is placed in an environment with humidity of more than 80% after opening, there may be obvious delixing phenomenon in just a few weeks, making the tablet soft and sticky, in which case its quality will be seriously affected and it may not be able to be taken soon.
Temperature: Suitable temperature can extend the storage time of vitamin C tablets. It is better stored in a cool place (temperature below 20℃). If the ambient temperature is high, such as above 30 ° C, the oxidation rate of vitamin C will be accelerated. Especially in the summer, if the unsealed vitamin C tablets are placed indoors without air conditioning, the decomposition rate of its active ingredients may be several times faster than in a low temperature environment.
Light: Vitamin C tablets should be kept away from light. Light accelerates the oxidation of vitamin C. If the unsealed vitamin C tablets are placed in a place where direct sunlight can reach, the color of the tablets may turn yellow within a few days to a few weeks, which indicates that vitamin C has begun to oxidize and deteriorate, and the efficacy will be reduced.
Tablet self-change judgment
Changes in appearance: Normal vitamin C tablets are white or slightly yellowish crystalline powder pressed into tablets. If the tablet appears discolored (such as a noticeable yellow, dark brown), has spots on the surface, is moldy, or is severely broken, it is likely that it has deteriorated and should not be taken. For example, when vitamin C tablets appear green or black mold spots, it indicates that they have been contaminated by microorganisms and must not be eaten.
Odor change: Normal vitamin C tablets generally have no odor. If there is a pungent, rancid or other abnormal smell, it may also indicate deterioration. For example, a smell similar to burning or rancidity of plastic indicates that the vitamin C tablets may have undergone a chemical reaction and their composition has changed.
In general, under good storage conditions (suitable temperature, moderate humidity, shelter from light), the opened vitamin C tablets may be acceptable for several months; However, if the storage condition is poor or the tablet shows obvious signs of deterioration, it should not be taken again.